Microphone not working for any connected device

The onboard microphone and the microphone in any device I connect will not work.

The microphone shows as connected in the audio properties under the recording tab. But when I speak no green bars appear. It shows as connected and working in any app that uses a microphone e.g. zoom or skype but again nothing is picked up when I speak. This happens for all devices I connect which have a mic. If I try any of the same devices on another windows 10 device, they work fine.

In device manager all devices under audio inputs and outputs show as working ok.

I tried removing and re-installing realtek audio but this didn't work.

Windows 10 Version 10.0.18363 Build 18363
System Model XPS 13 9360
BIOS Version/Date Dell Inc. 2.13.0, 14/11/2019
[Sound Device]
Name Realtek Audio 
Manufacturer Realtek
Status OK
PNP Device ID INTELAUDIO\FUNC_01&VEN_10EC&DEV_0256&SUBSYS_1028082A&REV_1000\4&32B8B7C&1&0001
Driver C:\WINDOWS\SYSTEM32\DRIVERS\RTKVHD64.SYS (6.0.1.8622, 6.26 MB (6,561,800 bytes), 19/03/2020 23:26)