am not entirely sure I understand what you mean as there is no 'test ion the connections window.
I have followed these steps: http://prntscr.com/evuvt8
and also these http://prntscr.com/evuwcn
if its something else please do let me know.
Also, in 2017 I have exported the site settings and imported it into 2015 to ensure they are both running the same settings and, althoughh 2017 works fine, 2015 still does not
also, both versions are accessing exactly the same sets of files
your continued help really appreciated :)