Launch the Mac in Recovery Mode (Hold down Command+R while booting the Mac).Make sure that there is no Dongle (Sentinel) Driver Installed. Open the Extensions folder from this location ( MacintoshHD/Library/Extensions/) then drag the Sentinel.kext file to the trash.
If you have an earlier version, it is not qualified to run on this macOS. The versions of Media Composer qualified to work with macOS BigSur began at MC 2020.12. This issue can be fixed by performing the steps listed below:
On a Mac running macOS 11.x (BigSur), the Sentinel driver system extension which is the extension used for the dongle, becomes blocked.
