We run several Dashboards from a dedicated workstation, of which one is PRTG. On occasion the browser automatic refresh fails, so the display goes stale. There is a very very small refresh countdown timer and current time display on the bottom of the browser window, but this is hard to see and usually cut off because the browser window is not maximized on the desktop.
FYI, we have tried IE, Firefox and Chrome and found the browser occasionally hangs with all three. To date, Chrome has worked the best.
I'm doing this on my MS SQL reporting dashboards, don't know how to do it on PRTG.