Fiat 500 L year 11/2014 power supply Diesel Engine 199B5000 Displacement 1598 KW77

The car in question comes from another workshop where the colleague for DTC P1541 has already replaced the oil pump complete with solenoid valve and oil bulb.
The strange thing that is driving me crazy is not the DTC P1541 but the fact that I can't get into the diagnostics (my colleague says he used to get in). To be on the safe side, I tried to get into the other ECUs and I got in, I postponed the job until today and to my surprise I can't get into any of the ECUs any more.
checked power supply and engine control unit masses and they are OK.
Tonight I try to enter engine diagnostics with the EOBD code reader and magically I enter the diagnostics intrigued I try again to enter diagnostics with both TeXa and Marelli and I do not enter.
I did a battery check and it gave me 12.86 volts efficiency status 96% charge status 100% with the car running alternator charged to 14.30.
I cannot give a logical thread to this.
Before I take the car to the exorcist I await your advice.