Further to the above I have noticed the following differences in the rhoconnect logs between the windows and linux setups:-
The linux rhoconnect log shows a status code of 401 for a userAuthurl get request. The Rhoconnect gem is version 4.0.0 and the rhoconnect-push package is version 1.2.2-2
I wonder if this reflects a mismatch between the rhoconnect gem and the rhoconnect-push package??
Rhoconnect-push v1.2.2 matches rhoconnect v4.0.0. App generated by rhoconnect-4.0.0 has 2 kinds of login methods: 'login' and 'rps_login' (you see both in controllers/ruby/application_controller.rb). The latter one is called by rhoconnect-push server when client is trying to register. In result you see their traces in logs. You should look at this doc Rhomobile | Setting Up for RhoConnect Push Service on Client Application and make sure that rhoconnect and rhodes configured as described there. On windows you use old 'and_login' staff that outdated and won't work for v4.0.0.