Error 13215 - China User Can't Join Meeting

I have a free Zoom Basic account for one-to-one meetings.

Desktop Zoom Workplace app version 7.1.5.84650.

My students have unique meet anytime Zoom generated IDs and connect from China via the app or browser.

On Friday 14 August there were no issues. I didn’t use it last week. Today they couldn’t join the meeting and got the following error message:

Error code: 13215 - unable to join meeting due to restrictions based on host account limitations. 

Creating a new meeting ID didn’t resolve the issue.

I haven’t changed anything in my account settings.

How can this be resolved?