Help getting snapshot setup in octoprint

Camera model
Logitech C270 and Logitech C920

What is the problem?
I have finally managed to get both cameras to stream to octoprint (and multi-cam within ) but i cannot get the snapshot to work.
Can someone tell me what URL should be in the snapshot box in octoprint settings?
Is it possible to use both cameras for this or must you only use one all the time?
What did you already try to solve it?
Have tried using:
but keep getting "Could not retrieve snapshot URL, please double check the URL' message

Logs (/var/log/webcamd.log, syslog, dmesg, ... no logs, no support) (21.8 KB)

Additional information about your setup (OctoPrint version, OctoPi version, ...)
OctoPrint 1.8.7
Python 3.9.2
OctoPi 1.0.0

Any help appreciated thanks