[ghtyr]

Not sure if this was answered or if it was figured out but I guess if anyone searches this in the future I'll add my fix.

When I had this issue, I had an email account set up on the phone, but for some reason, only the Calendar service was activated. I had to go into Settings > Passwords & Accounts > Selected my mail account which was Gmail > and turn on the Mail button which was deactivated.

Worked no problem after that.