Why does email app ask for Google Account Password on mobile data

[apwood]

I'm using a an S4, UK model GT-i9505, with all the latest updates from Samsung (ie on Lollipop), it is not rooted. (I shied away from that because it seemed complicated and risky though I have rooted previous devices).

I have my e-mail accounts set for manual sync only (gmail and hotmail but using the standard e-mail app).

Occasionally no,w when I try to sync my e-mails using mobile data (I'm on three mobile), it fails, and says "your google account has been removed from your settings, enter your google account password to authenticate the account". If I retry several times, even rebooting, it fails to work every time. I never actually enter the password because I'm uncertain which one is appropriate.

When I get home it syncs successfully over wi-fi - so it seems to me that the account has not been removed, and my phone has the correct password. So I'm confused by this message.

I wonder, could the password over mobile data be different, or a different authentication process be used? Could the fact it works quite often over mobile data an only occasionally fails, be because I'd previously authenticated over wi-fi, so it doesn't always ask me again to authenticate?

I can't remember if the e-mail app uses an app password, or my main gmail password with 2 factor authentication - how can I check this?

 

[B. Diddy]

Welcome to Android Central! Is the phone itself logged into your Google account? Go to Settings>Accounts. Is there a Google account listed? Tap it, and make sure your primary Google account is shown there, and that there are no sync errors.

 

[apwood]

Yes, its listed, and when I press sync there are no errors. When I tap the google account it shows me that the app data have been synced. I did that over mobile data just now. Google play books didn't sync, but it did over wifi (presumably I've set that somewhere to only sync over wifi). I have all other google syncing (other than e-mails) disabled.

Update: Decided to do some further testing:

Restarted the phone with wifi disabled and repeated the sync test. This time app data and google play books synced over mobile data, but the e-mail app gave the sync error. Turned wifi on and the e-mail app then synced successfully. Turned off wifi and tried an e-mail sync over mobile data - now no error.

Restarted phone again with wifi off, back into e-mail app with mobile data on but wifi off, email synced successfully - so now I'm really confused!

 

[B. Diddy]

Have you contacted your carrier to see if they have any input?

 

[apwood]

Not contacted carrier (three mobile UK) - I can't see how it could be a carrier issue?

 

[B. Diddy]

Mobile data is provided by your carrier, while wi-fi is from whatever broadband provider that wi-fi router is connected to. If you're only having the issue with mobile data, asking your carrier might be helpful.

 

[apwood]

Yet mobile data is working for everything else other than signing into email. I've fixed this by creating a new app password in my gmail account using my PC, and then adding that password to my gmail email account on my phone. No idea though why it failed on mobile data and not wifi.