Assuming I haven't made any forgotten changes to my install, but I believe this mod has a hotkey set to "J" for converting tiles. This seems to conflict with the game's default hotkey for connecting trains, also set to "J". I could not get my trains to connect until I figured out which mods had a shared hotkey setting (Earendel's JetPack and this mod use "J" as hotkeys). It wasn't until I cleared the hotkey for Asphalt that I could connect my trains with the hotkey.

As "J" is the game's default setting, perhaps changing the hotkey for the reconvert function to something else in warranted, as it completely overrides the game's function. (Jetpack seems to share the hotkey well enough.)

Thanks for the report, I'll look into it and try to find a better default key when I can. Or maybe I'll see if I can change the code to make it not conflict with the vanilla hotkey, if I can make it more contextual.

I just put out an update that should solve the issue.

You may see the train connection flying text when using the reconverter if you keep them on the same hotkey, but I added an offset to the reconverter text so they don't overlap.

The reconverter will now also try to detect if you are able to connect a train and ignore your input if so. This isn't perfect so if you're connecting stock to a train in a weird position it may fail but that would just mean it'd reconvert your held tiles anyways. I don't suspect this would be much of an issue for anybody.