Hi Yigit,

Credentials supplied in private content. The plugin developer site is at https://codecanyon.net/item/wp-cost-estimation-payment-forms-builder/7818230

To reproduce the issue, from the WP navigation panel select ‘E&P Form Builder’ (Await prompt as it is our test environment)
In the forms list, select the ‘preview this form’ icon which is the eye symbol (its next to the edit/pen icon)
You will be redirected to the main page (on a fresh install of Enfold this doesnt happen, the plugin works normally and previews the form).

Thanks in advance!