Hello,
For Steam users, the following steps usually resolve this kind of bug :
1. Delete didnapper 2 manually on your PC (delete the folder where the game is installed). Go to the steams folder where didnapper 2 in installed (usually in your programs/Steam/steamapps/common). it's important to not delete it by using Steam, because it will leave few files.
2. reinstall the game by using Steam.
3. Install the mod again and everything should work.