Just try changing between servers and keep rechecking...it took several server changes before the 5.7.893 showed for me.
I got it from staging 1. But it fails to update even though im at stock. I did notice after the update to 5.6.893 my webtop ver says unavailable if that is what causes the failure
Sent from my DROID BIONIC using Tapatalk
Check out this thread on how to manually update to 5.7.893
Easily Upgrade To 5.7.893, Keep Root And Webtop - RootzWiki
I did not want to go back to stock per those instructions, as I was on 5.6.893 and didn't want to have data wiped. I downloaded the 5.7.893 zip from the OP of that thread, then used Root Explorer to move it to sdcard-ext. Then I booted into stock recovery and installed the 5.7.893 zip. Now About Phone shows 5.7.893.