I replaced the battery, and now the phone is working fine. I replaced the battery with a spare I had because the battery in the phone was draining very quickly, so I knew it was worn out. I want to keep the phone for now because my uses are so basic.
Google search, Google maps, Gmail, etc. are all working fine now, but I am still getting the "Item not found" message when I try to install the new version of Youtube. When I tap the Youtube icon I get the message "A new version of Youtube is available. Install it now from Google Play". Then when I tap on "Install Now" I get the message "Item not found". I cleared the cache and data for the Google Play app, but I still get the message "Item not found" when I try to install Youtube.