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:
I hope this helps.