One of them refuses to enter command mode via X-CTU or Hyperterminal. Never gives OK response to +++, and holding the config button has no effect. I can see the data in/out lights blinking in response when trying to enter command mode with +++ but never an OK.
I have used the dip switch to reset it, but same problem.
I am pretty familiar with these, and the other XTend is behaving properly.
Have you tried resetting the modem in question back to default? If you can’t get it to accept a firmware overwrite, its likely that your XTend has a hardware issue.
If you wish to troubleshoot which part is causing the problem, you can use your other PKG to find out. You’ll have to dismantle both radios and swap the XTend modules. If you get the same behavior with the unresponsive PKG you know you have a bad interface board. If when you put the XTend module from the bad PKG into the good one and can’t get communication you know your module is bad.