I can not use my camera. It says that i need to connect a camera. What can i do?

Are there any AntiVirus, Disk Cleaner, Optimizers, Un-installers, etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal operation of the OS and may even Corrupt the OS requiring a Reinstallation. The Built-in Security of Big Sur is all that is required.

If you have tried everything in the linked article, you may have a hardware problem and will need to take it in for servicing.