Finger Print Scanner

Hey, i know this has been posted before. And i did read all the posts on it, but when i went to reply it came up with a warning messige, if that what you want to call it, saying that, that topic hasnet been posted for over 120 days. so i wasnt sure if i would get a reply...

So anyways this is my question. The fingerprint scanner on my Expo wont register my fingers. The weird part is, it DID work when i first tried to use it like 3monts ago. I really just set it up for s**ts and giggles. Never used it cuz i have to reason to lock my phone.

So anyways, a couple days ago, i felt like playing with the scanner again. I first tried locking to phone, but i wouldnt give me the option to lock the phone with the fingerprint scanner. The option where it say ON|OFF was grayed out. So i hit Detail, it brings up a screen where i had to put in a 4 didget code (and that another weird part. When i origionally did make up the back-up pin, it was a 6 didget code. But i got it to open up anyways.), then i brough me back to privious page. So i hit details again and it gives me the option to register my fingers. BUT IT WONT WORK!! tried all my fingers. My index finger atleast 10-15 times. WTF gives??? Did the sensor go bad? If it did, how can i replace it w.out replacing the whole phone...