We just experienced a weird bug with CentralNotice. This campaign was enabled and within its timeframe, and on the main campaigns list it was highlighted in green as active. Yet its banners were not showing to users and not listed on Special:BannerAllocation.
This persisted from about 1300 (when the campaign should have started) until 1334 UTC. Disabling and re-enabling the campaign had no effect, nor did removing and re-adding all the banners. What finally got it working was changing the priority from "high" to "emergency". Then on reducing it back down to "high" it continued to work as expected.
I can't recall this ever happening before.