Recently I was trying to setup an LAG LCAP bond between a SG500X Cisco Stack and a HP Procurve Aruba Stack.

HP

trunk 1/A1 trk2 trunk lacp

Cisco SG500x

Upon plugging the ports in , the Cisco Port Light would go Active and start flashing , the HP Port would briefly go sold on the Mode light for 2-3 Seconds then go Off

Status of both ports in config were both Off ( even though the Cisco port light was flashing )

After much trial and error , messing with STP and LAG settings , we moved to another port and it worked straight off , so it was a Dud port Cisco END!