Thanks for your reply.
I tried again even if I didn't think I could solve it, but redoing the procedure from the beginning I noticed that in the extraction of the ulmage file, there were two .buffalo files ( uImage-88f5182.buffalo and uImage-lsp.5.x.buffalo)
I tried with the one different from the one used for all the previous restores and it worked!
uImage-lsp.5.x.buffalo was the right file!
my nas now is working again
best regards
Giovanni