You are most likely triggering the overvoltage protection circuit in the PSU. Not all supplies may have that feature. You must be very careful running PSUs on 277v as most power supplies use 400vdc rated input filtering capacitors and rectified 277vac has peak voltages of ~390vdc. Cheap PSUs may have lower rated caps that may leak or explode if run continuously on 277v especially if your line voltage is on the hotter side of 277.

Short of upgrading filter capacitors and disabling the OVP circuit there isn't a way to properly run them directly on 277v. (you probably don't want to do that)

Best way would be to get a transformer with taps that will get you down to 240v