Prerequisites met but sometimes not unlocked. Check both saves: one unlocked and another not.
There are no major difference between these two saves as far as I can tell, other than a few relocation of outposts before attached to cities. Shouldn't make any difference.
Step by step of the bug
Step 1
Built 3 Commons Quarters and 3 Market Quarters in Nan Jing (finished on turn 10).
Step 2
Not prompted on turn 11.
Step 3
On turn 12, one auto-save prompted the civic but another didn't.
Prerequisites met but sometimes not unlocked. Check both saves: one unlocked and another not.
There are no major difference between these two saves as far as I can tell, other than a few relocation of outposts before attached to cities. Shouldn't make any difference.