The fingerprint sensor stopped working

@hamadakamal check your phones settings to see if the fingerprint sensor still shows. Something like this video will show you how to set it up. If you can't, or if your sensor does no longer show in settings, then you will have to consider replacing the fingerprint reader. Since iFixit doesn't yet have a guide for this, use the one from this site It does have the fingerprint reader guide listed. It is written in French but a browser like Edge or Chrome translates it very well.

While you work on your A21s, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has the same problem as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.