Master Enable button Not working - Back-UPS BE750

[Anonymous user]

I have a Backup-UPS BE750 and for the first few days the "Master Enable" button was working. 

However after doing some house cleaning and unplugging the UPS, the master enable feature button no longer lights up and the feature is not working anymore. The "Controlled by MASTER" outlets are now always on. I can hold the "Master Enable" button for 3 seconds and it will beep, but the LED for this button will not turn on.

I can confirm that button still works in the sense that if I unplug the UPS->Plug it back in->hold the "Master Enable" button for 3 seconds, I can configure the threshold and cycle through the 3 threshold LEDs, so the LED light is still working.

I have tried unplugging the battery for 20 seconds and plugging it back in and that has not fixed the issue. Is there anything I can do to fix this feature?