Go to Display settings and turn this option on.. Touch sensitivity when using screen protector..I never faced any issues with fingerprint sensor whether protector applied or not From the 4th security patch update that this device got from it's launch date. Now it opens 10/10 but it is not as fast as other devices in this price range.
Personally I don't understand why people cry about their Fingerprint Scanner of A50, I am using A50 From the 1st day when it started selling online and after using it for 3months they improved the scanner since then I never faced issues regarding fingerprint scanner. And now if you want expert advice then tell your prob to a techie or visit the service center you are just wasting your time here like an **bleep**. I wish I could attach video of my scanner working 10 out of 10 times here you poor souls would have cried after watching it.😂 By the way Reset cache after every update by going into recovery mode and re register your finger prints.