Hey there, try changing how you are logging in. At the login screen there should be 3 dots at the top right you can press that option and it should allow you to use a different login method there. If that does not help then I suggest the following:
Powering down the device and then starting it back up can often solve these types of issues.
Can you switch between Cellular and a WiFi network. See if the issue persists on both network types. If the issue appears only on one connection type, then it is an issue with that connection specifically. for Cellular you would need to work with the Cell data provider. For WiFi, you would need to look at the WiFi Network.
You can clear the cache and application data for the app by going into settings>apps>Heartstone>Storage(on newer versions of android) and press the clear cache and clear data buttons.
Sometimes you can clear out bad cached network data by resetting your battle.net account password via the website and then relaunching the game.
If that doesn’t work, let’s go ahead and uninstall, then reinstall the game application. I recommend restarting the phone after uninstalling.
Now this is not a step we recommend lightly but if you are comfortable with the process you can try doing a complete factory reset of the device and then load only core apps and the client. This means setting the device up as new and not syncing previous cloud settings.
That should solve most issues but of the problem persists it may be worth checking a different device and if everything works normally on the other device report the device specific issue in the bug report forums for further analysis by our QA teams.