Why schedule fail on Pinterest, despite successful same-day post & verified connection?

I'm experiencing consistent scheduling failures when attempting to pre-schedule assets to Pinterest via Adobe Express. The error message indicates a connection issue, however:

• I have verified the Pinterest connection multiple times.
  I successfully published a separate post directly to Pinterest on the same day as the scheduling attempts.
  This suggests the connection is functional, but the scheduling feature is encountering a specific, unidentified issue. There's no further context in the error message to help troubleshoot. Could you please investigate why pre-scheduled posts are failing despite a working connection and successful direct posting?