Michael, Thank you! Please, remove the link.
I really don't understand why & how come...
See the attachments.
I have been following the exact instruction described on the Nortel License doc (1.jpg).
Since I've no temporal Base Unit, I added one MAC address only during license generation in format capital letters only and colons (i.e. AB:4D:7B:CA:XX:YY:).
By the way I've successfully installed the demo license...no issues and still can't install the permanent one.
I tried to get Nortel’s European support but I was listening IVRs only

.
I downgrade and try adding the permanent license today with the following versions:
55x0_50011s.img, 55x0_510015s.img, 55x0_600005s.img, 5xxx_603009s.img and 5xxx_610007s.img.
The result is the same with all versions I tried.
I got lost. I don't know what's happening.
Does anybody know how to perform factory reset in order to try again?