You don’t really say what settings and where you checked.
Have you tried going in to the Control Panel > Recording > Select the microphone you use (is there more than one?) > Properties > “Device usage:” Is it set to “Use this device (enable) then in same menu > Advanced > Exclusive mode
Both
“Allow applications to take exclusive control of this device” and
“Give exclusive mode applications priority:
should have the check mark in the box.
Click O.K.
Fixed?
If not do the above with viber and in Cisco webex running and see what you get.
Long shot:
Some time unchecking, apply, OK closing and openning again and repeating with boxes checked fixes problem.
It would seem that viber and in Cisco webex are trying to use some other souund device.
Let us know how it goes.