Allow or Deny Windows and Apps Access to Camera for All Users using a REG file

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\CapabilityAccessManager\ConsentStore\webcam]
"Value"="Allow"

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\CapabilityAccessManager\ConsentStore\webcam]
"Value"="Allow"

Value string value

Deny = Off 

Allow = On

If camera app shows error "can't start camera error code 0xa00f429f <WindowShowFailed> (0x800706D9)", open services.msc and set "Windows Camera Frame Server" startup type to manual.

Source