Multiple APC boards

[Hakolsound]

Hello and thanks in advance for a great product.
I'm trying to set up two AKAI APC boards to be connected to a Intel-based Mac that hosts a Copperlan instance.
For some reason, the app only 'sees' one board but not the other.
they are shown @ the Intel-based Mac audio midi setup though.
Our setup includes three machines, a Mac that is directly connected to the two APCs and another two Windows 10 machines (main and backup) that are virtually connected, and the two boards with full midi cables.

Any ideas how to work around it?