Unable to download form list in Collect and error in Enketo preview

We have configured an ODK Central with local IP behind a firewall which is redirecting request to sub domain. We also configured SSL_TYPE as customssl and provided pem file as mentioned in the documentation. Now we can access the central home, configure project and forms. But the forms list is not accessible in ODK collect and enketo preview gives error “unable to verify the first certificate”.

Finally we resolve the issue, there was problem in fullchain.pem that we obtained from godaddy. After getting new SSL certificate for nginx and concatenating crt and pem file it is working in collect as well as enketo.