If the app reports you are offline, it means that the app cannot sync data with the Grosh servers. There could be 3 reasons
Your device is not connected to the Internet, check that other apps are able to do so.
The Grosh servers are not online. They are located in the Cloud at Amazon data centres spread across the world. Amazon has an excellent up-time record, so this is a very rare situation.
Your data cannot be synced with the servers due to a bug either in the app or the servers. Please report your situation to support using the Send message button on our home page, and we will try to fix the problem.