alfredhuangjie

The SAME PROBLEM HAPPENS TO ME TOO, I COULDN’T SOLVE IT.
THEY NEED YOU TO BUY A DEDICATED SERVER IN HOSTGATOR IN ORDER TO INSTALL THE ModSecurity FEATURE FOR YOU.
CONTACT FORM 7, WPFORM, JETPACK FORM. NONE OF THOSE WORKS UNDER FULL AMP.
Thinking about abandoning the forms, or hard code an AMP site from scratch.

What a scary update!
Go to your cpanel choose php selector then update to 7.1 and my site is back.

All-in-One WP Migration Import This one also helped me out.