Error: The preview could not load due to the iframe response being incomplete.

Hi there, I am trying to gain access to Themeco but do not have login credentials to start a forum. When trying to edit via Cornerstone on WordPress, error message: The preview could not load due to the iframe response being incomplete. Last week I updated PHP through Network Solutions. Can someone please help me log in and fix this issue? Thank you so much!

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