unfortunately I did not receive any help from Ketron Italy.
I have solved the problem.
I still had a copy of the previous version Audya4 53D,
have the firmware reset to 53D, then copied all the data from the system folder and overwritten in the Audya4 system folder.
Now everything works again.
You could not see whether a file was broken it to the files.
Everything looked normal.
Now I have again the latest firmware 54B and it works.