Hi Francesco68,
remember, that the ELU28 needs 16 timeslots, ELU5 only 8!
Have you the next 8timeslots free?
Yes? than follow the next strings:
you must deleted (ksexe)all extension on the board, than reprogrammed the ELU5 (cnboe), replace the board, programm the ELU28 and all extension again...