When manually specifying UPnP servers, the specified URL should be pointing at a UPnP device description XML.

With foo_upnp, the URL looks like this: http://<login>@<host>:<port>/DeviceDescription.xml

When foobar2000 mobile is fed a URL without the /DeviceDescription.xml and fails to load it, it proceeds to try one with /DeviceDescription.xml appended. However, for mysterious reasons, this fails for some people. The issue is being investigated.