Are you trying to connect to a wifi signal you don't have the password for? That won't work. It has to be your wifi router, or a public one that doesn't need a password. (And for a lot of those, you have to run the web browser [Chrome will do] and try to connect to some site, any site - then you'll get a page asking you to agree to the conditions for using that connection. Then you have to keep Chrome running - don't close it or clear it out of RAM.)
Oh - PP doesn't update Android versions. If it's a Sprint phone, you need a Sprint account (which means a Sprint card in the phone, so you won't be on PP any more) to get updates. Or you can just stay on the version you're on. Eventually (2 updates of Android version at the most) and the manufacturer will stop issuing them anyway. But that has nothing to do with wifi - my 2012 Sprint phone, which hasn't been on Sprint since late 2013, still connects to wifi just fine.