I have found a solution to my problem in a previous answer of Sherry:
<<<You can delete the existing configuration file by navigating to C:\Users\Public\Documents\Notation_3\Composer_3\ and deleting the existing MidiDev.cf3 file.
Now start up the devices that you want detected (eg. turn on the external stuff) and then start up Composer 3. It will start "clean" for device detection, and you should then be able to import your device description as usual.>>>
It worked for me as well, thank you Sherry, now I have successfully re-uploaded my .ins file. What I still do not understand is why from time to time this configuration seems to vanish ...
Anyway, just in case somebody should need the .ins file for the mighty Korg Pa4x (firmware 2.0) here it is ...
pa4x_v2_www.korgpa.sk.ins
Bye
Paolo
Torino - Italy