This error usually means that the Device Admin credentails entered on the Devices Tab in App Studio are either missing, aren't recognized or do not match the credentails set at the device.
Try these steps to correct the error:
1. Go to App Studio and login
2. Select the Devices tab
3. Select the Edit icon next to the device
4. Clear and re-enter the Device Username and Device Password
5. Select Submit
6. Try to install the app on the device again
If this does not resolve the install issue, please let me know.