Hi,
We received several users' posts to report the same error you have encountered. This might be an issue of the latest version of remote desktop app for mac, but there is no related official document at the moment since the update was just released several days ago.
If you would like to get back to the previous version, please try to uninstall the current app and then check if you can download and install previous versions from below link.
https://install.appcenter.ms/orgs/rdmacios-k2vy/apps/microsoft-remote-desktop-for-mac/distribution_groups/all-users-of-microsoft-remote-desktop-for-mac
Also, we suggest that you could post this error to the uservoice and let others vote for it to see if there will be any feedback from the product team.
https://remotedesktop.uservoice.com/forums/287834-remote-desktop-client-for-mac
Thanks,
Eleven
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