Idk about this phone specifically, but a common ducktape fix for shitty fingerprint sensors is to scan one finger onto multiple finger scan spots, even all 5 available. That should improve accuracy.

I'm using just the regular 7, but I had issues with mine to start too. I'm also using a glass protector. I found a post saying to enable screen protector mode. This is found in display settings, seen below.

Solved most of my issues with print detection immediately. My biggest gripe now is only being able to add 4 prints, which is just stupid to me.

I have the exact same problem moving from the 3a to the 6a. Why did they do this? The back sensor was so good!!

Are you using a screen protector? A lot of them make the fingerprint reader unusable.

The finger print reader on the pixel 6 is absolutely disappointing. I miss my mi mix 2 sometimes.

It works flawlessly for me while I struggled with the 4A fingerprint sensor. With the 4A I could get it to unlock roughly 25% of the time. The 7A doesn't work as well for my wife.

I have a theory of why it works so well for me. How oily/ wet are you fingers normally? Can you open a dog poop bag easily? My fingers are very dry and I can't open a dog poop bag without licking my fingers. My wife can open them no problem at all.

Yeah, it sucks. Recently moved from a 5 to a 7a and it's just terrible.

Maybe it will improve over time but chances are I'll switch to another phone vefore that happens...

Hopefully Google moves to a proper ultrasonic sensor like every other brand with the Pixel 8. I really want to move from Samsung so I can take advantage of rooting and stuff like Lineage, but the hardware is just... so awful.

Cost cutting disguised as new feature?

I never had the displeasure to actually use it, but apparently it was even worse on the Pixel 6. Pixel 7 and Pixel 7 Pro are basically the same as the Pixel 7a regarding the fingerprint reader.

Another "tip".... If your fingertip is dry, lightly moisten it, then try the sensor again.

My 7a fingerprint sensor with a Spigen glass screen protecter works fine about 95% of the time. When it doesn't, quick lick of the fingertip and that usually does the trick.

If you have a screen protector you have to turn on screen protector mode to get the fingerprint sensor to work at any sort of acceptable level. Even then it is not nearly as good as without a screen protector.

Mine was a bit patchy at first but now seems to be fine. I came to 7a from an ole' samsung s9, which was v reliable but in a different position (back) so it took some getting used to.

I'm using my thumb, because using a finger would mean going two-handed (prefer having it on the back tbh). I've only scanned one position, and I do find it's finicky in terms of needing to be in a certain position; I also find I need to press down more firmly than I expect, and it pretty much doesn't work if my thumb is damp or wet.

Maybe what @WhoRoger suggested will fix it, pls update the post if it does!