How permissions work
macOS — not Selv — decides whether an app may record your screen or use your microphone. You grant that once in System Settings › Privacy & Security, and you can take it back at any time. Selv can't capture anything you haven't allowed.
If capture has stopped
Work through these in order; the first two fix most cases.
1. Check the permission is still granted. Open System Settings › Privacy & Security, then look under Screen & System Audio Recording (for screen capture) and Microphone (for audio). Make sure Selv is listed and switched on.
2. Toggle it off and on again, then restart Selv. macOS sometimes holds on to a stale permission after an app updates. Switching the toggle off and back on, then quitting and reopening Selv, clears it.
3. Confirm capture is turned on inside Selv. A permission can be granted at the system level while the capture source is switched off in the app — check Selv's own settings too.
4. Restart your Mac. Worth doing once if the first three didn't help.
After a macOS update
Major macOS updates can reset privacy permissions for every app on your Mac. If capture stopped right after an update, that's usually why — re-grant it with step 1 above.
Still stuck?
If capture still isn't working after those steps, email support@selv.io and tell us what you tried and which macOS version you're on. That detail saves a round-trip.