Did you update from KK to LP? In any case, it's recommended that you wipe cache whenever you update so any KK junk won't interfere with LP. I'm on Verizon myself and the following method works for my phone although it's a T-mobile link. If the method doesn't match Sprint's, you can always search on Google so you do the right steps...
https://support.t-mobile.com/docs/DOC-14686
Note... wiping cache doesn't mess with your apps or files, but you never know... always good to have a back up just in case.