Similar to the "can't pick up" issue, although luckily replacing it with different tiles and then picking those up works.

Mod list is basically K2+SE, with a few QoL extras. I've used blueprint sandbox, and in there it works. Out in the real world, if I place it down however, I can't pick it up via mining or mark it for deconstruction.

QoL extras:
FNEI
platforms
Unminable Bots
LTN + LTN manager + SE LTN bridge
Constructron Continued / project terraverse + Dynamic Robot Queues
Factorissimo 2 (notnotmelon) - actually forgot I had that in :-D

Hmmmm, I had this issue with SE a while back but had it fixed with version 0.0.7.
It's been a while since that happened though so I can't remember what the initial issue was.
I'm not really free to fix this until next week but if you feel up to up, create a new sandbox save, place the flooring and save, then slowly remove mods until you can mine it again and let me know. I get the feeling it's a combination of SE+K2 or the platforms.

Started a new game with just K2 + SE activated, in addition to powered floors and creative mod (I didn't want to use the sandbox because you don't have a character body there and I wasn't sure whether that influenced the result)

Placed powered floor and solar floor, couldn't pick up or mark either.
Then tested: * SE standalone -> no luck * K2 standalone -> works * Vanilla -> works

I also found the discord message related to last time the issue occurred:
https://discord.com/channels/419526714721566720/1114943520940236820/1114943520940236820
And the prototype property related to it
https://wiki.factorio.com/Prototype/Entity#protected_from_tile_building

My days are pretty full as well right now, but if I find time, I can look into the code myself. I guess you'll be faster than me though.

Finally got around to looking into this and it seems that somehow the changes from 0.0.7 had been taken out so the fix I had put in place was no longer there.
Putting it back in and will upload the update shortly XD
Edit: Scratch the above, whilst the previous fix was missing, it also doesn't work. I think there's some changse perhaps in SE that are affecting it and there is likely another setting that needs to be marked.