Gmail not working for some iDevice users, Google investigating fix
According to an email sent to All Things D, Google said it is aware of the Gmail issues and is working on rolling out a fix, noting that affected users can follow a set of workarounds in the meantime.
A number of Apple iOS device users took to Google's product forums after receiving an error message reading âmail service imap.gmail.com is not responding." It is not clear what is causing the problem, but some have narrowed it down to an issue with either Google's servers or Apple's Mail iOS app.
Source: Google
Google notes that possible workarounds include installing the standalone Gmail iOS app or visiting the web client through Safari.