Try doing a soft reset. Hard reset may also be an option if that doesn't work. This happened to my 1520 but the solution I did was to update my router's firmware.
guys need your help i cant update my Lumia 1320 into windows 8.1 after I restore it, i try and try to click in the setting>phone update but it says "your phone is up to date. Last checked 2 seconds ago"