Hello,
On B3 switches, we used to have LACP enabled by default on all ports. On B5 switches, we no longer have LACP enabled per port by default, as there were complaints about LAG groups automatically forming when two links were connected between switches.
You will need to turn on LACP on the ports with command "set port lacp port PORT_STRING enable".
Regards,
Ryan Careno
Extreme Networks GTAC