Jun 02, 2017 08:54 AM|EvenMa|LINK
Could you try to access http://api.mydomain.com/help as my first reply? Does that works?
If not, might has some errors on IIS,I suggest try to install .Net Framework for IIS on the server by the following command.
Framework 4.0,4.5 ：
Framework 3.5,2.0 ：
And after above if still return 404,try to modify the configuration file such like the following configuration.
<modules runAllManagedModulesForAllRequests="true" />
If you have any other questions, please feel free to contact me any time.