Form preview shows server error 500

Hello I need help with my kobotoolbox deployment.
I made a deployment on a server behind a reverse proxy. THe reverse proxy is handling the SSL certificate. The deployement is stuck at wait for other 600 seconds
But I am able to login create forms and deploy them. The issue is when I want to preview the form

It shows server error 500

The logs does not show an error message just that it is ready for start up