Looks like it is a known issue to Apple and they are going to address the problem with a software update.
https://www.macrumors.com/2014/02/28/touch-id-iphone-5s-fade/
No. It doesn't. Set it up correctly and you'll be fine. I've had my 5s since launch and have seen the text "Try Again" around 2-4 times.
Over five months that's not bad at all.
Must be your iPhone.
I guess Apple need not bother with the fix that is about to come out then.
Let's all admit it, the fingerprint sensor on the 5s sucks. I have to re-register my fingerprint every couple of days. Everyone I know that has a 5s says the same thing. My wife has stopped using it all together. Meanwhile, the fingerprint reader on my thinkpad which is like 3yrs old still can read my fingerprint every time.
Why does this fingerprint reader on the 5s suck so bad?