The first thing that you should do if Mannequin completely breaks is of course contacting us either via Steam Community Forum, itch.io Community Forum, Mannequin's Discord Server, our Twitter account, or our e-mail. However, below are some easy-to-do fixes that often helps (these solutions usually apply to problems that is not reproducible by us developers):
To do this, right-click Mannequin in your Steam library, click
Local Files tab, and then click
Verify integrity of software files button. Steam will verify if there are missing/corrupt files present, and try to re-download those files again.
To do this, close Mannequin and delete these folders:
C:\Users\[Your User Name]\AppData\Roaming\Mannequinon Windows.
~/Library/Application Support/Mannequinon macOS.
After that, launch Mannequin again.
It might seems stupid but it has proven to work multiple times.