Not sure if this helps, but, this error message pops up when I try to host an existing save after I've enabled the mod.

The mod Quick Map Tag Teleport (0.2.4) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event QuickMapTagTeleport::on_player_left_game (ID 48)
QuickMapTagTeleport/lib/cache.lua:348: bad argument #1 of 2 to 'pairs' (table expected, got nil)
stack traceback:
[C]: in function 'pairs'
QuickMapTagTeleport/lib/cache.lua:348: in function 'remove_player_data'
QuickMapTagTeleport/control.lua:65: in function <QuickMapTagTeleport/control.lua:61>

Thought I had it - but I didn't. I will keep at it and hope to have a fix soon.

Thanks, looking forward to it!

OK - give this a shot.
https://drive.google.com/file/d/17gqpmbwIYp7c7UHLwtXmoZRNvJayO7ED/view?usp=sharing

You will need latest versions of base 2.0.32 and flib 0.16.2

OK - give this a shot.
https://drive.google.com/file/d/17gqpmbwIYp7c7UHLwtXmoZRNvJayO7ED/view?usp=sharing

You will need latest versions of base 2.0.32 and flib 0.16.2

So I've updated to the latest flib 0.16.2 I was running on 0.15.0 originally.
I installed 0.2.5 from ur link and was able to successfully load and host a multiplayer save.

However when I opened the map to test the quick teleport, this error message popped up and forced the game back to the main menu.

The mod Quick Map Tag Teleport (0.2.5) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event QuickMapTagTeleport::quick-map-tag_add-tag-input (ID 222)
QuickMapTagTeleport/lib/cache.lua:310: attempt to index field '?' (a nil value)
stack traceback:
QuickMapTagTeleport/lib/cache.lua:310: in function 'get_player_favorites'
QuickMapTagTeleport/lib/cache.lua:318: in function 'get_available_fave_slots'
QuickMapTagTeleport/scripts/gui/add_tag_GUI.lua:34: in function 'add_tag_frame_template'
QuickMapTagTeleport/scripts/gui/add_tag_GUI.lua:246: in function 'open'
.../scripts/event_handlers/custom_input_event_handler.lua:36: in function <.../scripts/event_handlers/custom_input_event_handler.lua:10>

ok - looking into it now...

So I found that it works fine for me, which admittedly does not mean a whole lot. So let's do a bit more sleuthing.
Could you share your save file and your factorio-current.log file from your multiplayer instance?
If you have any other info that you think might be relevant regarding your save file or any other aspect, please pass that along as well. Things such as how you created the save file, if you uninstalled the old mod and saved before installing the new mod, etc. I know it may be difficult to recall all those details now, but anything you may remember would be helpful.
I really want to get multiplayer up and running and appreciate your feedback and apologize for the inconvenience.

Save file link
https://drive.google.com/file/d/1pNxngmWptZEBq2wtV8Sd1QN9Lj-GfG8f/view?usp=sharing

factorio-current.log link
https://drive.google.com/file/d/1aRKEb7uJZrCsrjZ2RG-wvgeZW9m_npzW/view?usp=sharing

I believe I installed the old mod and tested it on Singleplayer first to see if it worked. Which it did. Afterwards I tried hosting a server with the save file and that was not possible so I removed the mod. I cant recall whether or not I saved during this process. But most likely I did not since when I test mods I don't save the game file because I want to experience it at the same time with the people I play with on a hosted server.

I recreated your save game and was able to make it work without issue.
(I checked the most recent mod I had sent and it worked fine, but I did find one potential pitfall so use this new link)

New mod file for you here:
https://drive.google.com/file/d/1OTbWm-3AvgeinxdbQPCXH4DS7xQZF_71/view?usp=sharing

How I went about setting up the multiplayer environment:

in multiplayer instance
drop latest QMTT mod into mods folder
start game as single player
save a new file: 2024.12.06 Universe FCWM 2 (or whatever you prefer)
exit the game completely

Then start a new hosted game using your new save

in client instance
drop latest QMTT mod into mods folder
connect to hosted game - it'll take a few to get synced

voila

Please let me know your result :)

I followed ur instructions and have now got it up and running on a hosted game working perfectly fine. :D Thanks!

Now I just need my friend to get on to see if it works properly for him. I will update you once he does.

So, currently a known issue I've run into is the favorite bar not fully working as intended. As in when u save and exit the game, either in a hosted server or singleplayer, and you boot up the save again the favorite bar is empty. The tag still remains on the map and when u right click the tag it shows that its ticked as favorite. You have to re-favorite it again in order for it to show up on the favorite bar.

Firstly, thank you for the feedback!
I see the issue with multiplayer, however, I do not see it with single player games, unless you were perhaps referring to the single player on the multiplayer game?
I'll work on this and get back to you as soon as I can. Thanks for your patience.

Yes, same exact save as the one I've provided previously. Has the same issue whether I host it as a multiplayer game or I load the game file as singleplayer.

Ahh - that's the issue I think. You are passing around the save file and that save file has the issue within it.
Send me that save file prior to deleting the mod if you could so I can take a look at it.

Manage your mods and delete the mod in all your saved games. Or delete the mod from the folder and edit your mod-list.json. Make sense?

Here you go.
https://drive.google.com/file/d/1G8ovNPyqAebv0zKZadfWQHOkiwXuMaEQ/view?usp=sharing

Also I created a new singleplayer save just to test it out. And I couldn't even click the quick teleport in the favorite bar. This error messages pops up.

The mod Quick Map Tag Teleport (0.2.5) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event QuickMapTagTeleport::on_gui_click (ID 1)
QuickMapTagTeleport/utils/map_tag_utils.lua:214: attempt to index field 'character' (a nil value)
stack traceback:
QuickMapTagTeleport/utils/map_tag_utils.lua:214: in function 'teleport_player_to_closest_position'
QuickMapTagTeleport/scripts/gui/fav_bar_GUI.lua:215: in function 'handler'
QuickMapTagTeleport/lib/gui.lua:391: in function <QuickMapTagTeleport/lib/gui.lua:377>

Update, This error message pops up if I have editor extension enabled when I try to click the teleports.

1. Yes, I have confirmed that the teleport function does not work when in Editor Extension mode. This straight up causes an error and crashes the save.

2. I created a new singleplayer save (freeplay, default settings) and added tags to favorites, saved and quit and reloaded the file in singleplayer. This works fine. Then I tried to host the same file in multiplayer. The favorite tags are no longer showing in the favorites bar.

There were some other issues with Editor Extensions - not sure if that has anything to do with the whole situation or not. I'll take a look at that possibility tomorrow.
Thanks for your input. Really appreciate it.

FYI - just figured out why player favorites are not being saved. I will have an update tmrw

Yeah I think because editor extension puts the player in like a ghost mode? or smth cause the player model doesn't show up when editor extension is enabled.

No rush. Whenever ur free.

I haven't tested fully yet - but here it is:
https://drive.google.com/file/d/1hgE4ZXFRcOzSvwAbG0DB3MPnoeIu1G0c/view?usp=sharing

FYI - your log file will be large. But we can fix that soon enough

Tried it out, seems like its been fixed. Nice! Great work.

btw - you gotta mean map there :)

Hahaha thanks. A lot of trial and error with friends to see what mods work for us and our playstyle.