Ok ... so I couldn't help myself and rebuild the linodes and yes ...looked at the problem again ...
It turns out that NGINX is resolving to the wrong server block (namely the default block) even if the domain that is entered is correct. The strange thing is that it resolves to the wrong server block from only my office .... when try it from my house, it does it correctly.
Now, I can solve this by forcing NGINX with default server, but that can't be the right thing to do ... why is NGINX not resolving to the server block corresponding to the domain name that is entered in the browser ? And why is it doing it wrong only from my office location, and not from the house ? That's really strange.... Any ideas ?