trying to update to big sur 11.6, but my comouter wont take my passcode.

Hello Blake0714.

Thanks for reaching out to Apple Support Communities. We understand that the password for your Macbook Air is not accepted when attempting to update the macOS. We will be glad to assist.

First, try restarting your computer to see if that helps. Next, start up in safe mode and try the update: Start up your Mac in safe mode

If you still need help, try resetting the password your Mac and update: Reset your Mac login password

Hope this helps.

Cheers.

Hi Blake0714.

You are most welcome!

Take care.