These days, most of us are facing SE T630 trouble, here is the solution for such problem, if your T630 is "approved by IDA to use in Singapore" kind of phone and after flash/downgrade/unlock it is locked to a specific GSM band and you are depending on a lazy team's GSM equipment then don’t worry, and follow the following instructions.
1. Flash it with
Given MCU.
2. Uncheck “Protect Sa When Flashing GDFS”.
4. Initialize security block with OTP imei.
And Enjoy…
[PaWaa]