When you’re developing a custom service in D365 Finance / Operations at some point you will need to access the endpoint URL (WSDL link) to test your integration.
An example of the endpoint URL for a development environment is: https://usnconeboxax1aos.cloud.onebox.dynamics.com/soap/services/UserSessionService?wsdl .
If you have an issue with the service that you created you will get a “page cannot be displayed” error when you open the WSDL endpoint URL in a browser. Since no additional information is displayed in the browser this can be very frustrating to resolve. When this happens the first place to check for clues is the environment event log.
Open event viewer and go to Application and Services Logs > Microsoft > Dynamics > AX-IntegrationServices > Channel:Operational (Microsoft-Dynamics-AX-IntegrationServices/Operational)
In the Operational Event Log, Details tab, you will find exception details such as issues with Data Contract serialization. I recently saw a case were someone used the same name for two different members of a data contract. This caused an System.Runtime.Serialization.InvalidDataContractException where “multiple members with the same name in one type are not supported“. In this case adjusting the data members names in the data contract class and re-building the service group resolved the issue.