I used a Samsung Note 8 for around 5 year's then bought another phone a Samsung Note 20. I put my SIM into the Samsung Note 20 and it registered straight away. While I am in Cyprus I want to put a local SIM into my Note 8, I fitted a SIM and entered the PIN code and for some reason it asked for the PUK code, I've never come across this before, when I entered the PUK code it it said I was unsuccessful, so dismissed and used it without the SIM, in the status bar the notification says "Invalid SIM" I then put the SIM into my dual SIM Note 20 and it registered straight away. Why is the Note 8 telling me that the SIM is Invalid? I would be grateful for any help.