Hi Johannes Gloria,
Welcome to the Microsoft Q&A Platform! Thank you for asking your question here.
We understand from your query that you are experiencing an issue while trying to connect a microphone while using the virtual machine.
Please verify below checks and settings:
Open the Remote Desktop in VM then navigate to Local resources-> Settings - In Remote Audio Recording, enable option Record from this computer then click OK.
In the virtual machine, access Services by typing "Services" in the Start menu. Find the Windows Audio service, right-click on it, and choose Properties. Change the Startup type to Automatic and start the service if it isn’t already running. Then, restart the virtual machine and reconnect using the modified RDP settings. Open Device Manager by right-clicking on the Start button and selecting it from the list. Expand Audio inputs and outputs to see if the microphone is listed. If it’s not, check that your Remote Desktop or remote connection settings are set to allow microphone redirection.
Please check Local Computer Policy->Computer Configuration->Administrative Templates->Windows Components->Remote Desktop Session Host->Device and Resource Redirection:
Allow audio and video playback redirection - Enabled or Not configured Allow audio recording redirection - Enabled or Not configured
Computer Configuration > Administrative Templates > Windows Components > Remote Desktop Services> Remote Desktop Session Host > Remote Session Environment > RemoteFX for Windows Server 2008 R2 > Configure RemoteFX - Enabled
Computer Configuration > Administrative Templates > Windows Components > Remote Desktop Services > Remote Desktop Session Host > Do not allow supported Plug and Play device redirection - Disabled
Please verify above settings and try to connect again. If you have any further queries, please do let us know. If the answer is helpful, please click "Accept Answer" and "Upvote it" as it can be helpful to others in the community.