I'd suggest doing a hard reset first - hold down the power and home buttons until the white apple shows up. If it doesn't fix it, try that again - sometimes it takes more than one reset.
Otherwise, I agree a modem/router reset would be next. I've had my wireless printer suddenly not "see" its queue even though the printer appeared to be connected to the wifi. Took a day's worth of struggle to discover all that was needed was a modem/router reset, as Davidra says.
The other possibility is an app conflict. If nothing else works, be suspicious of the apps you've installed from the time this problem surfaced. They don't always play nice with each other or with iOS, especially if there are a lot of apps installed. Remove them in reverse order and see if the problem goes away. Then you can re-install all but the offending app.