I really doubt that this is the cause of the problem --- Post updated --- I uploaded the version without reducing the size of the map, because I made a copy before reducing the size.
Using the zip files don't work. For me the small version #1 and the big version #2 of the "bugged" files work if I unpack the zipfile and put the levels/polish_roads_v2 folder to C:\Users\[yourname]\AppData\Local\BeamNG.drive\0.28\levels. If you try to let BeamNG unpack the Mod in the Mod-Manager, you get a folder structure like that: C:\Users\xxx\AppData\Local\BeamNG.drive\0.28\mods\unpacked\polish_roads_v2\levels\levels\polish_roads_v2 In the Logfile you find things like: 11.75523|D|GELua.core_modmanager.initDB| mountEntry -- /mods/polish_roads_v2.zip: MN2D9XPFH : polish_roads_v2 12.05329|W|GELua.core_levels.| info.json missing: /levels/levels/info.json 12.05345|E|GELua.core_levels.| No entry point for level found: /levels/levels. Ignoring level. It seems that you have to check the folder structure somehow.
I have updated version 2.3 (Small size). The problem is still that in the map selection does not appear when it is in zip, I know that.
Ok so, I think the problem has been fixed (Tested by a couple of people). So version 2.3 has been released. Enjoy the game!