MapDotNet UX Services utilize the popular Log4Net logging system. By default, errors are logged in the file mdns.log.xml. For "Studio Engine" this file is in "bin" folder of Studio. For the web services, file is directly in the "Services" folder.
To change the location of this file for the engine or the web services, edit the "Log4NetConfig.xml" file in the "Studio" or "Services" folder. Change the "value" property of the "file" element appropriately.
By default, errors are logged for the map and query (Feature) services but not for the edit (FeatureUpdate) or data sources/transfers (Admin) services. See the "Service Configuration" section of the Services Administration page for more details.
If you are experiencing trouble and the error in the log file doesn't help you fix it, visit the UX forum and post your issue. We'll do our best to post a response quickly.
You can also preview your maps configured for a given UX service by accessing the viewer.aspx page at the root - e.g. http://localhost/MapDotNetUX[your product version]/viewer.aspx