I have had this problem off and on since Friday. You select "Activities" in either modern or standard and the headers and search box show up, but nothing is listed? I thought it might be an extension (adblock or something) in Chrome so I tried in IE, same problem. If you go to the main dashboard you can see your most recent activity and then step one by one through past activities, but to do a search to compare a route in the main activities list...nothing shows up.
Seems its not my machine/browser. Anyone else having website issues?
