Why is my laptop not displaying external webcams?

Check if external webcams compatible with device:
Check laptop manufacturer’s website if the external webcams in question are compatible with the device.
Check if camera drivers are up-to-date:
Go to computer device manager and check if camera drivers are up-to-date with latest manufacturer version.
Check if external device settings are enabled:
Go to device settings and look for options enabling external devices. They may have been disabled due to virus protection.
Check if virus protection is blocking device:
Run an anti-virus scan and make sure that the external webcams are not being blocked by the virus-protection software.