404 Error when saving forms

Hi,

I get an 404 error when trying to edit or even make a new form.

I’ve updated wordpress and contact form 7 plugin to the latest version. I’ve also tried to downgrade to the 4.7 version of the contact form 7, but still get the same 404 error landing page no matter what I do.

Please advice.

The page I need help with: [log in to see the link]