With newer devices (from the end of 2017?), Reprogramming using a key combination no longer works! There is software from Alinco (the so-called O-Setup software) available to switch bewteen radio types (frequency ranges).
In the software you can only select the DJ-500(TB), DJ-500 T and DJ-500E types. The Open Mode type DJ-500EX can’t be selected.
Now comes the trick: Set the „Freq.Set“ checkbox and „Write“ to the radio. Afterwards the key combination works again and you can select also Mode4 ( DJ-500EX )
see frequency-modification-dj-500 for the Mode and Frequency range overview.