iMessage and FaceTime is not working in My MacBook Pro after installing Big sur

I just asked the same question to tech support from the computer company where I purchased helped me to work through. https://support.apple.com/en-us/HT208386

NadimRouf wrote:

iMessage and FaceTime is not working in My MacBook Pro after installing Big sur

If you can't sign in to your iMessage account or FaceTime on ...