It sounds like this is related to a change in the required permissions for managing or creating apps in the Marketplace.
For the greyed-out “Server to Server OAuth App” option and creating new apps: You will first need to ensure you have the appropriate permissions. Please review the requirements here: https://developers.zoom.us/docs/internal-apps/
For the previously created apps (“No access” error): Can you first check if assigning the necessary permissions (as detailed in the link above) resolves the issue?
Please let us know if assigning the permissions fixes the problem.