I've seen several other forum entries for this issue in SharePoint Designer 2013 when accessing my SharePoint sites. It will pop up the message
The server could not complete your request. For more specific information, click the Details button. repeatedly until I force to kill the SPDESIGN.EXE from the Task Manager. The message is very vague and does NOT tell you what is the root of error.
When you click Details button, it does NOT any information as well.
The solution on other sites is to enable anonymous authentication on the Sharepoint Web Services site. I've done that on my web app, as well as the SharePoint web services app, with the same error message. I've tried doing an
IIS reset, as well as following the instructions on this link. I'm not sure what I'm missing.