N3048 port-channel down when we add the vpc configuration

hi,

we are trying to connect 2x esxi hosts (with vDs and LACP) to 2x DELL N3048 switches using MLAG,

we have the same port-channels on both switches with identical configuration. If we use the show interface port-channel command, all the links are active on the port-channels but when we use the command vpc XX inside on the port-channels, the links on one switches become inactive

Channel   Ports                         Ch-Type  Hash Type Min-links Local Prf
-------   ----------------------------- -------- --------- --------- ---------
Po51      Inactive: Gi1/0/6, Gi1/0/15   Dynamic  7         1         Disabled

any advice is welcomed... :)

thanks for your support,

Marcos