I've never had a problem with cell phone access on forms through Atahualpa until this month. (Dec, 2018).
Visitors are complaining they can't log in, and can't use any form on my site if they enter with a cell phone. I checked with my phone and they're right. If you try to enter data in any field, the cell phone's keypad pops up for a split second then it disappears before you can click a letter.
No other way to enter data without that virtual keypad. No problems if entering data with laptop/desktop.
Plugins have been disabled to make sure it isn't a compatibility issue.
The only thing I know that changed is Wordpress sent me an email letting me know my site auto updated to the newest version of Wordpress. I thought I had that feature turned off, but I was wrong.