Some users cannot see or import custom visuals on the cloud service

I have a client that has several PowerBI Pro users that connect from all over the world.

Recently, a serious issue has risen: some users suddenly could not see custom visuals, nor import them from pbix files, not even in their workspace.

When they publish a report with custom visuals from the Desktop version of PowerBI to their workspace in the online service, the custom visual simply disappears. If they try to import it, nothing happens (no error messages on the ui, but the visual isn't imported).

By checking the browser console, I see a lot of errors for these users when I load a report with a custom visual or try to import one, here's an example:

These errors do not happen for users that don't have this problem.

• What could be going on here? Some further info:
• Problem appeared relatively recently (days/weeks ago), custom visuals were working fine for all users before
• The same users that have the problem on the service do NOT experience any problem in the desktop version
• If they publish a report from desktop to the service, custom visuals disappear from the report
• Problem might be region-related: a user that has the problem reported not having it when connecting through a VPN to another region. We do not have a reliable way to test this however

Any help and suggestion is appreciated, because this is seriously affecting several users and geopardizing our contract with the clinet.