Windows 10 Build 10166 for Slow ring not avaiable??

[Windows Central Question]

twice a week ago i have install Windows 10 TP Build 10166 for Slow ring but but to un avoidable problem i revoerved Win8.1.
but before a 2 day back , i again congfigured my LUMIA 535 Dual for Windows 10 Build 10166 for Slow ring but
my phone Updateed to WINDOWS 8.1 Update 2 BUT now Why Windows 10 Build 10166 for Slow ring IS NOT availble for my phone??????
whenevr i chech is say... up to date..

 

[aximtreo]

Change to the Fast Ring setting, do a soft reset of your phone and then check for updates. Keep in mind that if you want to upgrade to the new 512 release, you will have to have 166 loaded before the 512 will be loaded.

It might be a good idea to download the Lumia Recovery software and bring your phone back to 8.1 baseline and then start the upgrade process.