Edit: Solved! I don't know if all of this was necessary, but here's what I did:
1. Updated the schema in the API Flow, since it was missing a field.
2. Updated the API Flow to remove certain fields which may have caused issues with an API call.
3. In ION API, refreshed metadata for ION API Flows.
4. In Active Connection Points, paused the stuck connection points, then deleted the top message in the processing list.
5. Unpaused the Connection Points.
6. Messages appear to be flowing through again! ... But then they got stuck again and I had to repeat steps 4 and 5. I'll see if I can figure out if there's something in the payloads that's causing it to get stuck.
I've got a Data Flow that ends in connection points which use an API Flow, and I noticed that they have tons of requests that are piling up in Pending and not making it through to Received or Sent.
What might the cause of this be?
All three of these connection points are for the same API Flow, just with different parameters.

