When I reboot the mic for the webcam dissapears
Disappears from where?pavucontrol
Is the webcam showing on the configuration tab after a reboot?
If there, is it 'Off' or set to 'Analogue Input'?
Is it showing on the 'Input Devices' tab?
If yes, is it the correct MIC input that is selected? It should give an indication which MIC is displaying.
Is it muted on that tab?
Is it set as 'fall-back' device?
Check the above settings and provide pics where appropriate to show us what you see.