My finger print sensor not working

@samwelmhilu you are not giving us much to work with here. It would be great if you could tell us what it is doing, what you have checked and what you have tried.

First check the basics. for that use the suggestions from this Samsung site. After that you need to dig a bit deeper. Try to do the hardware diagnostics by going to dial and enter *#0*#, then select Sensors and sub options in Fingerprint Scanner. See what that shows you.
Should that not work either you can try to do a "wipe cache" after booting into recovery mode. The last option would be to do a hard reset, just remember that with that, you will lose all of your files that are stored on your phone. Make sure that you back everything up first before contemplating a hard reset.
If none of that works or the sensor is not responsive, you may need to consider replacing it.The S10 fingerprint scanner is located on the front of the screen. Check this video Smontaggio Samsung Galaxy S10+ at around the 2min mark. It is the same location as the S10