You also need to enable LACP on the MLAG ports in SW1 and SW2
MLAG Port SW1
en mlag port 1:1 peer "core-sw2” id 1
en sharing 1:1 group 1:1 algorithm address-based L3_L4 lacp
MLAG Port SW2
en mlag port 1:1 peer "core-sw1" id 1
en sharing 1:1 group 1:1 algorithm address-based L3_L4 lacp