Seems, AT&T which has started releasing Lumia cyan to Lumia 1520 in US is still not making it available to Lumia 1520 with Dev Preview. That may be due to the known issue of Devices running Dev Preview and BitLocker encryption, where you need to roll back your device’s firmware to Windows Phone 8.
Now, in case you are already running DP on your Lumia 1520 and you are on AT&T, we would suggest to wait a bit and let Microsoft sort this out than rolling back to Windows Phone 8
- Because, a rollback can be a messy affair as there are basic differences between the way apps installation (MicroSD card) and back up is handled for Windows Phone 8.1 and Windows Phone 8.
- If you are already running dev preview now, and roll back, you will be tempted to try Windows Phone GDR1, when it comes out for devices enabled for dev preview. So, why to go through so much of a hassle.
In case you still want to roll back to Windows Phone 8, here is your help.
Do let me know what you think?