1) Remove all accounts from your device under the Android Settings -> Accounts
2) Go to Android Settings on your device and enable “USB Debugging” (phone setup in this link)
3) Connect your device to the PC with USB cable:
a) If you are running Windows download the helper application and run it
b) Otherwise make sure you have ADB installed and execute the following from a command prompt:
adb shell dpm set-device-owner com.ccswe.appmanager.deviceowner/com.ccswe.appmanager.receivers.DeviceAdminReceiver
4) Re-add your accounts
Unfortunately the Android security model does not make it possible for one application to enable/disable components for another application. This makes sense for standard applications because you wouldn’t want a competing application to be able to disable yours. That is why CCSWE App Manager requires device owner privileges in order to achieve this.
It is possible to activate device owner on a device without a factory reset.
That being said if you are encountering errors with device owner activation then the simplest way to resolve them is to factory reset the device and activate device owner as soon as possible (ie: right after adding a Google account to download the application from the Play Store).
Once you have activated device owner you will need to use the ‘Uninstall’ option inside the application in order to remove device owner and uninstall the application.
Some devices (confirmed Samsung Galaxy S8) do not properly report an error when there are non-Google accounts on the device that are preventing activation.
If the Windows helper application times out or the adb command never completes you should try removing more accounts.
An application on your device, such as Samsung’s Secure Folder, has already created additional user profiles on the device. You will need to disable these applications prior to enabling device owner.
There are still accounts that you need to remove from the device. If you have already removed all your Google accounts then check for device manufacturer accounts (ie: Samsung) and temporarily remove those. Keep removing accounts until you are successful.
The most common cause of this error is that you still have one or more accounts on the device that you need to remove.
There is already an application with device owner on the device.
If this application is not CCSWE App Manager (Device Owner) then you will need to uninstall the application before you can activate device owner.