You can test the internet connection by going to 'Settings' in the app and choosing 'Network diagnostics'. If you see check marks all over, that means you have an active internet connection. Not all internet connections are of good quality. Even if you see check marks everywhere after the diagnostic, the app may still not synchronize the data. In this case, if possible, use your mobile's personal hotspot. A 4G connection is more stable than a wifi connection in most cases.