Hi, the first step is to put your Mac in Recovery Mode, go to utilities and then terminal: input the prompt that was given. When you do you'll get the system log saying that the action has failed
"-bash-3.2# system-override legacy-camera-plugins-without-swamera-indication=on
Volume on disk3s5 failed to mount
This is an encrypted and locked APFS Volume; use "diskutil apfs unlockVolume" system-override: failed to mount volume (disk3s5)"
When you receive this message you then want to input: disk3s5 + Enter. Your Mac will show you all the disk3 in the system, look for the in parentheses -(disk3s5), if it's different for you, you'll probably need to look for the one that says "Locked".
When you have located the (disk3s5), you'll have the option to input your password for Mac, it'll say something along the lines of "passcode" that's just the Mac password. Once you do that press enter and it will go from lock to unlock. You'll get the prompt statin it was unlock as well. After that you can restart your Mac.
Test it out and let me know if it helps you. I can do a video recording if you need it.