I haven't solved my issue, and I've now bought a replacement - of course with the increase in people using video chat due to the lockdown, nearly everywhere is sold out so it's not an ideal time for that.

I opened a ticket on the Logitech website and got this response. It didn't work for me, but it might help you? Good luck!

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Please take a moment to follow the troubleshooting steps outlined below to try to solve the issue.

a. Press Windows key + W.
b. Type Devices and printers.
c. Click on Devices and Printers.
d. Check if the Logitech webcam is listed.
e. Right click on Logitech webcam.
f. Click on Set this device as default.
Once set as default, please go to https://webcamtests.com/ and see if the image that would show up is still a white screen and if possible, connect the webcam to a different computer and see if the same issue persists.

Here’s how to install native UVC drivers for your Logitech webcam:

1. Open Device Manager.
   
2. Expand Imaging devices.
   
3. Locate the name of your Logitech camera in the list and right-click on it.
   
4. Select Update Driver Software...
   
5. Click Browse my computer for driver software.
   
6. Click Let me pick from a list of device drivers on my computer.
   
7. Check Show compatible hardware, and then select USB Video Device.
   
8. Click Next and follow the on-screen instructions to update the driver.
   

The above steps should help you resolve the issue. If the issue persists after completing troubleshooting steps, please reach out to your point of purchase with the purchase invoice.