SOAP Service URL gives "500 Error" "There is a problem with the server" on the browser.

Hi,

I have made a custom service on dynamics 365.
The json url for the service works fine but for the same service, the soap url does not work.
At first, I thought it was doing it with all the soap services so I tried a system service but it worked giving an xml code on the browser.

This was the system service I tested : 
https://usnconeboxax1aos.cloud.onebox.dynamics.com/soap/services/SysHealthPingServiceGroup?wsdl

And this is my service :

https://usnconeboxax1aos.cloud.onebox.dynamics.com/soap/services/EDIServiceGroup?wsdl

Here is a screenshot for what it displays in the browser :


How do I fix this issue?

Best Regards,
Muhammad Ozair Naeem