Is this the dialog you see?
It means that Reader for Android encountered a problem and could not complete the operation that you asked to do.
There are a couple of things you could try.
- Make sure that you have updated to the latest version of Reader for Android. The latest version as of March 20, 2014 is 11.1.3.
- Make sure that your Android device has internet access. (Open a web browser and go to any web sites.)
- In Reader, tap My Account in the home screen.
- Tap SIGN OUT (at the upper right corner) to sign out.
- Tap SIGN IN to sign in.
If you still have a problem,
- Go to Google Play.
- Find the Adobe Reader app.
- Tap UNINSTALL to uninstall the app.
- Tap INSTALL to re-install the app.
- Launch Reader.
- Tap My Account in the home screen.
- Tap SIGN IN to sign in.
If it still does not work, you may need to reboot (power down & up) your Android device. Hopefully, it's not a hardware problem with your device.