I cant even sign in to update!
Have you tried holding your Vita power button and resetting it? Then see if it works.
Also sometimes the Vita will reset WiFi settings for some reason, you may want to set up your WiFi again and make sure it's set properly first.
If both those don't work I am assuming it's the connection not the Vita but you won't know until you make sure or test it on another WiFi connection.