Find Full Text feature doesn't work with Endnote x8

Hi,

I am also experiencing problems to find full text with my Endnote x8 library on PC. I have bibliographic access to full text from my institution. I can authenticate (ID and password), and request find full text (right mouse clic on the reference). Surprisingly, even for the same journal (eg Neuron), it works with some references but not with others (not found), during the same EndNote session. This is something that I can not understand, because the settings are obviously the same. Would anyone have a clue regarding this unreliable outcome?

Best,

Xavier