The camera permission never appears
Chat video call online free difficulty: you press the button, nothing happens, and no prompt arrives. Most people conclude the site is broken and leave, and almost nobody is right about that.
What's happening is that the address got refused once before (by you in a hurry, or by somebody else on the same machine), and a browser that has been told no won't ask twice. It fails quietly instead, which is the worst possible behaviour and has been the standard one since permissions were first specified.
The fix is the padlock or the little icon at the left of the address bar. Open it, find the camera entry, set it back to «ask», reload. Thirty seconds, and it works on every browser there is.
Two related things while we're here. The permission is granted per address, so an address carrying www and the same address without it register as two separate places and will ask twice. And a link tapped inside a messaging app opens a small browser living inside that app, which handles cameras badly and forgets grants between sessions.