For a simple update, you don't need diagbox.
Also an automatic coding is only possible, if you have an online connection with diagbox and that's only possible with V9, a Servicebox account and you have to buy a token (42€).
You can try checking, if the blind spot option is just disabled and activate it again.
I would suggest the version 7.57.
I don't understand. How do I not need a diagbox for a simple updates? What do you mean?
As far as I know, 308 II (2013-2017) can be telecoded up to diagbox 7.49.
Is it possible that after checking for SMEG update in diagbox but offline the blind spot will just turn on?