This irregularity was resolved as of 22:00 UTC. Enterprise users can use Replay to recover lost data. Premium users will have to use the different standard endpoints to retrieve lost data.
Posted Apr 23, 2020 - 22:53 UTC
We have identified that some activities may not have delivered via the Account Activity API starting at 2020-04-23 19:30 UTC. We are actively working on a fix, and will provide details on how to recover data once the irregularity is resolved.