FIrstly, the MXP 1000 devices are past their End of Support Date (31 May 2018), so I would recommend that you update them with something that is more current and supportable.
Secondly, F6.x is a very old software load for those devices (the most recent was version F9.3.6), so there may be unexpected bugs you're encountering in such an old software version making it somewhat incompatible with the newer software based endpoints (like the DX80). Which software version are you running on the DX80? There were some fixes for talking to the older MXP devices in one of the latest software releases for the DX (latest as of the date of this post is CE9.6.1).
But otherwise, to get some more information on your issue:
Do the MXPs auto answer when you call one from another? Or is it the DX80 that doesn't answer when you call it from one of the old MXPs? Or the MXPs don't answer when you call from the DX80 (and only the DX80)? Are you dialling each of the endpoint types the same way. or is there some difference in how you are doing it (ie, via a directory entry vs manually entering the number)? Do the MXPs ring at all, but just don't auto answer, or do they not ring when dialled?
Wayne
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