Avaya 1416 does not work on a IPO 400 digital module

[ejvl]

Hi,
One of our customers use a Avaya IPO 500 (v8).
1 IPO 500 16 digital station module ( 10 44) latest firmware.
1 IPO 400 16 digital station module (10 44) latest firmware.

Avaya 5420 works fine on both modules.
Avaya 1416 works fine on the IPO 500 16 digital station module but doesn't work on the IPO 400 module.
The display gives a message "language file required" and another 1416 station the display have a message with only the letter A.

We try different 1416 stations, on the IPO 500 module no problem, on the IPO 400 module, doesn't work.
We've replaced the IPO 400 module for test, but no result.

Is there any solution for this?

In advance thanks.