I posted an ad to the Community Promotion Ads - 2019 thread, and the ad has had the requisite 6 votes for several days, but as far as I can tell it has not yet run on the Q&A site. Just wanted to check to see how the timing works, or whether there's something else I need to do to trigger the ad to run. Thanks!
1$\begingroup$ I don't know, but here's an old Meta Stack Exchange thread about how long it would take for 2016's ads to start showing up (When will 2016's community promotion ads start being shown?). My take away is that it is likely to take a while. $\endgroup$– gung - Reinstate MonicaApr 22, 2019 at 18:29
https://stats.meta.stackexchange.com/ads/display/5551 it seems to be already active, it just gets no clicks.
Well.... one now, since I just clicked on it. Now it says 0.07 clicks per day. So that means it was online 14 or 15 days ago (today is May 2th). That is about 1 or 2 days after you posted the add.
Beyond that, I have no idea if, how often and where those ads are shown. I have never seen them.