I just had bought a new iPad Air with a cellular modem. 1PW seemed to be working fine on it until the data allowance ran out on the cellular modem. After this happened I reconnected to the internet via WiFi.
When I then opened 1PW, the display was empty and showing a message telling me it was syncing and that my items would appear there after it had finished (just like when you install 1PW for the first time). However ths never went away and even swiping the 1PW off the multitask list to close it and restarting the app didn't fix it. A reboot of the iPad did though.
I don't know if this was because iOS got its knickers in a twist over iCloud sync due to the sudden suspension of cellular connectivity or if it was a 1PW problem but I thought it worth mentioning. I was worried I'd lost my data there for a bit