PC 5548 not receiving LACP PDUs

Hi,

I've connected two PowerConnect 5548 via the 10G interfaces and created a port channel.

But one of the switches is not receiving LACP PDU (it is also not receiving LLDP PDUs) and therefore the LAG is not established.

Creating a static LAG works.

Both switches are configured equally.

interface tengigabitethernet1/0/1
 channel-group 1 mode auto
!
interface tengigabitethernet1/0/2
 channel-group 1 mode auto
!

Switch1# show lacp statistics tengigabitethernet 1/0/1
te1/0/1 LACP statistics:
      LACP Pdus sent:                75
      LACP Pdus received:            0

Switch2# show lacp statistics tengigabitethernet 1/0/1
te1/0/1 LACP statistics:
      LACP Pdus sent:                90
      LACP Pdus received:            45

Any hints on how to debug this? What could block the PDUs on Switch1?

Thanks.