Your analysis on the sense code and the ACTPU not requested bit is correct.
Can we get the pdlog and configuration? If you don't want to attach those entire files, "show snasw pdlog id 1766 detail" and "show run | incl snasw" should be enough.
What I'm looking for is what kind of link this is, and how you have the port configured.
There are certain types of links that we determine must be dependant LU only, so we don't let the link come up if it won't be usable. It sounds like the Stratus controller is LU 6.2 only? Ray noticed that the incoming XID does not have a CPname, and we suspect this is the problem SNASw has with it. Since you have migrated from subarea (IBM 3745) to APPN, a CP name is required for APPN routing
We think you may be able to work around this by adding a conntype to the snasw port. Unless this is a "dial out" link initiated from the host, probably adding "conntype dyncplen" to your snasw port that the downstream connects in on will fix the problem, as SNASw will create a dynamic CP name (starting with @) for the downstream device. That should make it look like a different link and adjacent CP type, one which can support LU 6.2 and does not require the ACTPU requested support.
If that doesn't work, or you have any question about this, please collect the pdlog and configuration requested above.
