Hey Peter, which steps did you try so far?
To list a few possible solutions:
- Verify the game files in Uplay, to check for potential issues
- Make sure you start the game with admin privileges
- if the folder in which the game is saved is a cloud drive (e.g. OneDrive), this can also be a problem. Make sure the saves are stored on your PC directly
- Check your antivirus, make sure it's not blocking the game or certain files. Try completely disabling it for a test
- Disable all non-necessary background programs before starting the game