This is a bit of a long shot and i am not sure you can access the secret menu at whatever stage you are stuck on with the error message on the smart box.
Hopefully the box as already connected to your wifi network after the error message is shown on your TV screen.
Perhaps try pressing the Home button on the remote 5 times, quickly followed by pressing the FF button 3 times then quickly press the RW button 2 times and if it does open the secret screen then update the software (even though the software version may be the same currently on your box).
Thanks for the secret menu tip off. I managed to access it even with this error and selected a factory reset via here after trying the reset button previously without success, and this time it worked. I now have a working box again.
Hi I’ve had my replacement box for 2months and still not being able connect and says , Activation plugin not downloaded:-4 glad I have a Amazon Fire Stick as a back up much easier to use out of the box
NOW TV BOX SET FOR RECYCLING