Before continuing if you see a "No Camera" message in the Studio:

Please make sure that all programs that might be using your camera/microphone (such as OBS/vMix, etc.) are closed and then please click on the "Try again" button.

If that still doesn't help, please refer to the remaining of this article:

"Invalid Resolution" and "no camera" errors may be a result of an unsupported video source, or resolution, as well as a connectivity issue.
Typically, if you can see your camera in the browser before going live, and get an error only when trying to go live - this is a connectivity issue.
We recommend to first test for camera compatibility and then check for any connectivity issues.
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Test your video/audio sources and supported camera resolutions:
​https://loola.tv/camtest/

Some popup blockers and firewalls prevent Loola from working properly.
Use the following link to test your browser connectivity:
​https://test.webrtc.org/?turnURI=turn%3Aturn.loola.tv%3A80&turnUsername=janususer&turnCredential=januspwd&stunURI=stun%3Aturn.loola.tv%3A80

Your test results should look similar to what's shown here:

If both the UDP and TCP tests fail, and/or the Relay Connectivity test, then you may not be able to use Loola.
This is typically resolved by disabling/changing firewall rules that are blocking UDP packets, and/or STUN/TURN protocols, as well as disabling any popup blockers.
Loola uses port 80 for both STUN and TURN handshake (should be open by default in most firewalls).