Hello!
Several times we got the same fault with S1720-28GFR-4TP and S1720-28GFR-4TP switches. Some times when power fail occurs, the switch don’t power on after resuming the power. And switch stay turned off even when power is on it. Plug off and plug in of the power cord didn’t restore the functionality of the switch.
The solution is to plug off the power cord or turn off the mains of the switch for several minutes (about 5 to 10). I think that it can be some problems with capacitors inside the switch that are release its power during that pause and after that switch work fine.
