Besides a user proxy which may be accessed via Internet Explorer>Tools>Internet Options there may be a proxy set on the machine itself.
To find out open a command prompt and type:-
netsh winhttp show proxy
This usually comes back with Direct access <no proxy server>
If, however, there is a proxy listed it can be removed by typing:-
netsh winhttp reset proxy
Having a machine proxy set may prevent connections to the Hosted Applications service.
Reviewed on 02/03/2018