As of Feb 18 2025 if you have transistioned to Altium Develop colaborating with a standard A365 or A365 Pro user has some limitations. Sharing invitations from A365 to Altium Develop are not currently being received by the invited Altium Develop user.
Workarounds are required:
The Altium Develop user needs to download the A365 project while connected to A365 workspace, then switch to Develop to edit files within the project.
The Altium Develop user needs to use a git shell or Git GUI, i.e. TortqoiseGit to pull or commit changes from and to the A365 workspace.