Hello
Please open Hyper-V settings in your Hyper-V manager and check the enhanced session mode option under Server > Enhanced Session Mode Policy and User > Enhanced Session Mode. If the enhanced session mode is already enabled, uncheck the option and click OK to clear settings, then enable enhanced session mode again.
Connect to your VM with an Enhanced session, switch to the Local Resources tab, click "More" and select the "Other supported Plug and Play (PnP) devices" option.
If the issue persists, run services.msc from the Start menu to open Services and restart the Hyper-V Virtual Machine Management service manually.
Additionally, see if the Remote Desktop Connection client on the RDP user machine is up to date. Older versions of the client may not support the redirection of certain devices. Check the device manager on the Hyper-V host to ensure that the microphone and camera are recognized and installed correctly. Make sure you have installed the latest drivers for the devices.