If anyone runs into this problem, this might be the answer.
"Hi Oscar,
The Param Xmit/Rcv parameters must be matching on both of the units being polychained as it determines whether in CC or NRPN the two devices will be communicated for parameter changes. Usually, NRPN messages offer more control than CC and can carry manufacturer/product-specific commands. Therefore it is the preferred mode for poly chaining between Sequential products.
It will also be good to check whether both the units are loaded with the same OS version (displayed upon power-up).
Hope this helps!
Best,
Gabby
Sequential LLC"