Fingerprint sensor calibration required

This can be a hardware problem. So please contact nearest customer service centre.

This is a very common problem with the A series phones.
First you have to check if you have the latest software update installed in your phone. For some users updating fixes this issue.
Second, check your fingerprint sensor via the diagnostic mode (dial *#0*# and choose sensor).
If your sensor is alright then obviously the issue is NOT in your sensor i.e. hardware.
For most users who report this error it comes with software faults.
If software update doesn't help and if your sensor is working correctly, then you will have to do a factory reset.
It will make this error go away.

This happens when you replace either the display or fingerprint sensor. Did you?

Try googling.

Contact to a customer service , I am also using a galaxy A51 device, but the fingerprint is working normally, from a single tap it unlocks the screen