JabRef version 3.6 on Debian 8 Jessie
Steps to reproduce:

1. click on Help inside Jabref
2. A browser opens at https://help.jabref.org/it/

Obviously, this depends on the fact that my operating system is in Italian and that there is no documentation in this language.
Could you make sure that, in the absence of documentation in a particular language, Jabref points to the documentation in, for ex., English?

Thank you very much for your attention,
Domenico