I entered my home site url and got my test results. When it got to the screen shot, though, it was showing my mobile site, not my desktop site. Any idea what's going on and how I can get it to test my desktop site?
Try going to the advanced settings and checking the "preserve user agent string" box. Usually WebPagetest will add a PTST to the UA string so testing can easily be filtered out from analytics but sometimes that triggers an over-sensitive server-side UA sniffer.