Connecting Bluetooth Headset 500 to PC does not enable microphone

[derpinguin7]

I purchased a HP Bluetooth Headset 500. product number 2J875AA and connected it to my PC via Bluetooth.

The output works fine. It registers as a device called "Headphones (HP Bluetooth Headset 500 Stereo)" in the Windows Settings for Sound -> Output. I can listen to music or any other output.

But I haven't yet been able to use the microphone on my PC. The device registers among the input devices as "Headset (HP Bluetooth Headset Hands-Free AG Audio)" (why a different name?) and I can choose it as input device, but there is no sound transmitted *at all*. Not too silent or weak, but no data at all. If I open Audacity, for example, choose the headset as input device and start recording, Audacity does not record anything (not even silence).

When I go into the headset's "Device properties and test microphone" menu and press "Start test", I can scream as high as I want, I will always see "The highest value we saw was 0 percent".

• Yes, the volume is set to 100 percent
• I have tried uninstalling the device drivers and restarting my PC. The device is recognized again and the exact situation returns.
• I have checked in my "Microphone Privacy Settings" that all apps are allowed to access this microphone.
• I have checked that there are no conflicting microphones active.
• I have tried the absolutely useless Windows Troubleshooter.
• I have checked if the headset works with my Android Phone, and yes, it does: The microphone records my voice without problems, even if I walk into a different room (to rule out the possibility that it's my phone's mic that is recording)
  
  So what should I do now? Is this headset useless for video calls?