Xperia:SIM Lock
A SIM Lock is basically a special condition that a cellphone carrier places on the phone, locking it to their network. This also locks the bootloader and prevents fastboot from working. It doesn't make your phone completely useless, but it does neuter it a bit (at about the same level as the R800at); you should be able to make other modifications that don't require bootloader or fastboot, such as rooting. SIM locks used to be fairly rare, but a lot of users recently have been buying Xperia Plays from AliExpress that are advertised as unlocked, only to get them in hand and discover they're actually still SIM locked.
If you're trying to follow instructions on here and no amount of troubleshooting is making fastboot work for you, and you're not sure if the phone is carrier locked, here's how you can check:
- Open the phone dialer app.
- Enter *#*#7378423#*#* and a service menu should appear.
- Go to Service Info > SIM Lock
- You should see something like this:
- [] Network 0
- [] Network subset 0
- [] Service provider 0
- [] Corporate 0
- [] SIM 0
- If there is an **X** between the brackets on Network, Subset, or Provider, and the counter is at 0, then your phone is SIM locked, and you have no further attempts available to unlock it.
So if you're SIM locked, what can you do? Unfortunately, very little. Even when a carrier unlocks the network, the bootloader and fastboot will remain inaccessible. The only known successful thing for unlocking it and restoring full functionality at this point is using SETool. This is a difficult program to get ahold of and get working properly. Supposedly this tool can unlock the bootloader on the R800at as well, and install fastboot to it. If you have a working copy of this tool and are willing to share, and can demonstrate how to use it, please make a post in the /r/XperiaPlay subreddit and contact Antnommer!