We used to be able to use the mobile app for iOS without a problem. Now if we go to log in and click the Google Login button, the immediate message is a 403 disallowed_useragent message.
Logging in with Google on desktop works fine. Also tried logging in through Safari iOS and that authenticated fine as well.
Not sure if StackExchange community is the best place to post this but since it's the primary Salesforce iOS app, I'm sure others may have experienced this.