Hey, let me try to help you with this.
First of all, make sure that your wintermod files are in the correct folder.
It should be in this folder: Docuents\ETS2MP\mod or in Documents\ATSMP\mod. You might have to create the folder called mod.
Now, if you do have the mods in the correct folder, make sure that you have the right mod.
Here's the links to the mods:
Base - https://sharemods.com/zdmxhwpikdrh/frosty_7_3.scs.html
Heavy winter addon - https://sharemods.com/lkrniy3494jf/frosty_heavy_winter_7_3.scs.html
Physics - https://sharemods.com/n1uo9p1j5hj0/frosty_physics_7_3.scs.html
Lastly, if nothing here works, check the checksums of the mods by using HashTab to make sure that none of the files are corrupted.
Here's the checksums:
frosty_7_3.scs
MD5: 81265DD2C3FA44F4FADA50C6A8EDE1AB
SHA1: 20003EF0248D65B1FB33B9D6476F3691DA147210
frosty_heavy_winter_7_3.scs
MD5: CF2103EE23E4012DFB812E66466DCD44
SHA1: BB73E2EF212C5520880EB41895AA9FF00E10C6E7
frosty_physics_7_3.scs
MD5: 3DA71F1B32B2352427B85BE35CA71799
SHA1: B28375AAFE75F44DA9904952ABAF574A141E1D8A
I hope this helps.
Kind Regards,
Grubby