Inputs 5 & 6 not working on 888-24s, Pro Tools TDM 5.1.3

[Batman_60]

Hello,

I am attempting to resurrect an OS 9 Pro Tools Mix system on a G4 (my income studio has a PTHD3-10 system).  I've owned and successfully used several 24 Mix + systems on OS 9 and 10 in years past, but this particular G4 has never been a Pro Tools machine before.  I recently purchased a used Mix Core card and two used 888-24s and have installed PT 5.1.3 and it recognizes the interfaces and outputs audio from all 16 outputs.  However inputs 5 and 6 on both I/O interfaces do not work.  When I feed signal to these inputs before the computer is on and the I/O is basically in "stand alone" mode signal appears on the meters, but as soon as I open a session no input appears on those channels (5-6 on the A interface, 13-14 on the B interface).

I'm running OS 9.2.2 with only 512mb of RAM.  The interfaces are connected to the Core card with a Y cord.  I don't have a spare Y cord to test, but I have tried several Digi-Link cables to the interfaces from the Y cord.

I have tried using each interface by itself without the Y cord, and two different DigiLink cables.  Each time I trash the Digi Setup, DAE Prefs and Pro Tools Prefs so that Pro Tools asks about interfaces on each launch.  No difference - channels 5 and 6 on either interface will not see input signal.  But, again, they do see signal when in "standalone" mode (computer off).

Any thoughts on this being a PT software bug or OS conflict?  My Mac OS 9 skills are long dormant, so no amount of oversimplification is too much.

Thanks in advance for your support.