In the last week or so, I have repeatedly had to re-add the workspace URL for Windows 365 (the "subscription URL" collected from windows365.microsoft.com) to Microsoft Remote Desktop for Mac. The iss...
Mine has not disappeared for about a week, now. Version 10.9.2 (2147) on macOS 13.5.2. Not sure if updating to the latest version fixed it, but if you haven't updated to 10.9.2 (2147) on the App Store yet, see if that solves the problem for you.