Cox Speed Check Latency Error

After clicking the "Check Speed" button on the Cox Check Speed web page I get a message in a small black dialog box that says: "Latency Test Error Latency test returned an error while trying to read the latency file." This started happening after a Cox technician came out to fix an internet problem I was having (very slow internet early in the morning). Prior to his work, I did not get this error. This happens regardless of which web browser I use (Internet Explorer, Chrome, or FireFox). However, I can run the internet speed test at speedtest.net, no errors are reported, and the speed reported is correct (around 64 Mbps download). All other web access seems to be normal. I have a *cabled* connection between my desktop PC and the router (not using wireless). The cable modem is a Motorola/Arris SB6141 (ie it is a DOCSIS 3.0 modem) -- but remember, I was able to successfully run the Cox Check Speed test before the Cox technician came to fix a problem. Both the cable modem and the router were properly power cycled after the Cox technician made the repairs. I cleared the cache on my web browser but that did not eliminate the error message. No other changes have been made to my PC. Does anyone know why I would be getting this error, and what a possible solution might be? Thanks