Greetings Fabio,
The option for directly converting an EndNote library within Reference Manager is for EndNote versions 7 and earlier. EndNote 8 and higher use a new library structure that won’t allow for the direct conversion. If you visit our website here- http://refman.com/support/faqs/Import/faq3.asp you’ll find instructions that walk through the required export from EndNote to a text file that Reference Manager would then be able to import.
Jimmy McColery
Customer Technical Support Representative Scientific
Thomson Reuters
Phone: +1 800 336 4474
ResearchSoft Product Support