It's most likely still processing all the new files that got added, have patience and wait for it finish loading.

Reset your server filters, worst case scenario check your internet firewall.

Open the game by running the Talvisota: Winter War app in Steam, the launcher will automatically clear any conflicting mod files on your computer.

Make sure that Rising Storm 2 is installed, and the mod is installed on the same drive.

This means that your Windows installation is potentially missing the newest Python files. Just open Rising Storm 2 directly instead of the launcher.