You can try a clean install. That should get rid of any corrupted or modified files, old mod residue, etc.

Uninstall the game via Steam, then go to the install directory, default should be:
C:\Program Files (x86)\Steam\steamapps\common

If there is still a Valheim folder, delete it manually (this will not affect your saves, they are stored somewhere else).

Reinstall the game via Steam.