Troubleshooting

A delivery is "Blocked"

Waiting for credit or a plan. The activity says "waiting for credit" or "the team doesn't have a plan yet". It carries on by itself after a top-up, a plan or a trial starts.
Queued behind the engineer's limit on concurrent work. It starts by itself when a slot frees.
A step failed with no fallback ("… failed and has no fallback step"), or went back and forth too many times between the same steps. Fix the cause if there is one, then press Resume on the delivery's card (optionally saying what changed or what to try), or reply resume (or resume: <what changed>) in its Slack thread. It picks up at the step it stopped on. Consider adding a failure route to the workflow for next time.
A platform problem, such as credentials being rejected. The activity names it. Reconnect the integration, then Resume.
"current step no longer exists": the step it was on was removed. Avoid this by duplicating workflows that have deliveries in flight.