Working on two computers creates duplicates

Hello, I work on the same documents from two computers (home and office). I have Mendeley on both and both are linked to the same account. However, I am realizing that if I add citation from one computer, the other does not associate it correctly to the same reference. It believes that the reference is missing from my database, which basically means that it creates duplicates (or, if I cite the same reference again, they will appear as two different references, i.e. 2000a and 2000b). Is there something I am doing wrong or is that a bug? Thanks, Nicolas