Why on screen fingerprint doesn't works

@dyskeycombey I suggest that the very first thing to do, is to check on Samsungs sitefor their suggested fixes.

If those do not work it is possible that this is a bad fingerprint reader. Since iFixit does not yet have a guide for that, use something like this video If you prefer the written guides check this one out.

Replacement sensors are widely available at plenty of online stores. Just make sure that you purchase one for your particular version of the A30s

While you work on your phone, 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.

Repair is War on Entropy!