For 4 days now, my samsung Galaxy Ace mobile has not worked. The cell consistently displays "unregistered SIM" and "no service". Googled a fix - take out battery and SIM card, replace after few seconds... did not work. What's up?
Could be a faulty SIM card. I'd advise you to take your Ace to your nearest Koodo kiosk and ask to try one of their active SIM cards. If this works, then you can purchase a replacement SIM there for $10 ($20 if on prepaid, but that one comes with airtime credit). Depending on the age of your SIM, you may get a free replacement (but I can't promise that).