I switched to PDU mib and received a response:
snmpwalk -v2c -c LiebertEM 10.24.0.48 -M /opt/librenms/mibs:/opt/librenms/mibs/liebert LIEBERT-GP-PDU-MIB::lgpPduTable
LIEBERT-GP-PDU-MIB::lgpPduEntryId.1 = Gauge32: 1
LIEBERT-GP-PDU-MIB::lgpPduEntryUsrLabel.1 = STRING: MPH Rack PDU
LIEBERT-GP-PDU-MIB::lgpPduEntrySysAssignLabel.1 = STRING: 1
LIEBERT-GP-PDU-MIB::lgpPduEntryPositionRelative.1 = Gauge32: 1 Count
LIEBERT-GP-PDU-MIB::lgpPduEntrySysStatus.1 = Gauge32: 1
LIEBERT-GP-PDU-MIB::lgpPduEntryUsrTag1.1 = STRING:
LIEBERT-GP-PDU-MIB::lgpPduEntryUsrTag2.1 = STRING:
LIEBERT-GP-PDU-MIB::lgpPduEntrySerialNumber.1 = STRING: 535055G104C2013MAY300225
LIEBERT-GP-PDU-MIB::lgpPduEntryRbCount.1 = Gauge32: 3 Count