How to fix Microsoft Remote Desktop giving RDP error when trying to add Workspace on Mac

Trying to add a Workspace on a client's Mac machine to access software through rd web client and keep getting this right after credentials are entered. We are trying to access an application on a Windows 2019 terminal server.

There are two accounts on the machine and both give this error. It happens immediately. The website referenced in the workspace is accessible from both Safari and Chrome. The OS version is Montery. Having them upgrade to Sonoma to see if that fixes it. I can find no instance of this exact error anywhere on the internet, that's why I came here.

Thank You for any help you can provide.