Hi John, nop, the “key” field is “key__classes__content_row__container”, i named with “key_” my key fields and without “key” the names, so for any field i allways have:
Field keys must start with “field_”, if your using “key_” then that’s probably part of your problem.
It’s easy to miss in the field settings section https://www.advancedcustomfields.com/resources/register-fields-via-php/
$field = array (
/* (string) Unique identifier for the field. Must begin with 'field_' */
'key' => 'field_1',