as i said earlier, you can't open/view files located in .bc folders with the Viewer app,
you need the Boxcryptor Classic from here:
Yes, they are displayed right now in the File Browser, but this will be removed in the upcoming update, so that we do not confuse users anymore.
Regarding the error you have, i would suggest to check your proxy settings, if you are connected via wi-fi. Just select your wifi from the list in Settings, and at the bottom you should see the proxy settings.