Hello Leonard Schwenk
Welcome to Microsoft Q&A Platform, thanks for posting your query here.
The error message you are seeing is related to the certificate in the .rdpw file that has expired. Unfortunately, there is no way to set a time limit to the file or prevent the certificate from expiring.
However, there are a few options you can consider to avoid having to distribute a new .rdpw file every 4 months:
Use Azure AD Application Proxy: You can use Azure AD Application Proxy to publish the Remote Desktop web client and allow users to access it through a secure URL. This way, you can avoid distributing the .rdpw file altogether.
Use Azure Virtual Desktop feed URL: You can use the Azure Virtual Desktop feed URL to distribute the Remote Desktop web client to your users. This URL is unique to your Azure Virtual Desktop deployment and does not expire. You can find the feed URL in the Azure portal under the "Overview" section of your Azure Virtual Desktop deployment.
Use PowerShell to automate the distribution of new .rdpw files: You can use PowerShell to automate the process of distributing new .rdpw files to your users every 4 months. This way, you can avoid having to manually distribute the files.
I hope this helps!