Thank you.
I have tried it and it works for some references, but not for others.
I have find the both cases: some references (in fact, many) in my endnote reference list had already the DOI, but it did not appear in the updated reference found by EndNote, and I could not include DOI in some references, because it did not appear in the updated reference. I have checked if they correspond to old publications or less common journals, but these are not the case.
Anyway, this solution is faster than that I used, although I have to check reference by reference for accepting updates and click the save and continue button every time.
Thank again
Pilar