Setting Device Owner doesn't work

[akama-aka]

I only have one account which I can't remove anywhere (which makes sense I can't delete it because its the main & default user). If I click on "Remove/Check Accounts" I'm just getting the account & Autofill Settings Tab opened which has completely nothing in it. As I tried to continue and entered the "adb shell dpm set-device-owner com.bos.oculess/.DevAdminReceiver" command I got this Issue:

Exception occurred while executing 'set-device-owner':
java.lang.IllegalStateException: Not allowed to set the device owner because there are already some accounts on the device.
        at com.android.server.devicepolicy.DevicePolicyManagerService.enforceCanSetDeviceOwnerLocked(DevicePolicyManagerService.java:10995)
        at com.android.server.devicepolicy.DevicePolicyManagerService.setDeviceOwner(DevicePolicyManagerService.java:9639)
        at com.android.server.devicepolicy.DevicePolicyManagerServiceShellCommand.runSetDeviceOwner(DevicePolicyManagerServiceShellCommand.java:257)
        at com.android.server.devicepolicy.DevicePolicyManagerServiceShellCommand.onCommand(DevicePolicyManagerServiceShellCommand.java:87)
        at com.android.modules.utils.BasicShellCommandHandler.exec(BasicShellCommandHandler.java:97)
        at android.os.ShellCommand.exec(ShellCommand.java:40)
        at com.android.server.devicepolicy.DevicePolicyManagerService.onShellCommand(DevicePolicyManagerService.java:11433)
        at android.os.Binder.shellCommand(Binder.java:1093)
        at android.os.Binder.onTransact(Binder.java:913)
        at android.app.admin.IDevicePolicyManager$Stub.onTransact(IDevicePolicyManager.java:6329)
        at android.os.Binder.execTransactInternal(Binder.java:1369)
        at android.os.Binder.execTransact(Binder.java:1300)