Hi,
I’m also having the same issue with Contact Form 7 and WP Mautic Form Integrator.
As you mentioned, I’ve checked that with OAuth 2 and OAuth 1. But no luck for me. I still encountering the blank screen for Add New option.
Thanks in advance!
Versions:
Contact Form 7 : 4.5.1
WP Mautic Form Integrator : 1.0.2