Can you please let us know if you have created any mobile applications
in the Sitefinity instance you're trying to connect to? Please note that you should have at least one application present, to which Sitefinity Box can connect to.
In addition, can you please elaborate on "I have tried it on a SF 6.0 site and a SF 5.0 site."
- please note that the mobile app builder feature is available with our Sitefinity 6.0 release, and was not present in the previous versions.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items