Hi @K_T11 welcome to Zwift forums.
During the installation process, you should have been asked to give permissions to the Documents folder. Did you allow those permissions? If no - the app will not start up correctly. Please check the permissions using the steps in this Support article.
Alternately: try unistalling / reinstalling the game app:
1 Search for “Zwift” in Finder, and delete all the folders and files that come up.
2. Manually download and install the app.
3. This time - be certain to allow write permissions.
Would you let us know if either of those fixes your issue?