Troubleshooting

An engineer didn't reply in Slack

You didn't mention the app. In channels (including thread replies), mention @YourEngineers. DMs don't need it.
The app isn't in the channel. Invite it.
You're not a member. The engineer replies that it only takes requests from members. Ask an admin to invite you, or add your Slack ID on Members.
No name and several engineers. It asks who it's for. Use name: ….
No plan or out of credits. The engineer says it can't start or has paused.
The engineer is PAUSED or retired, or at its concurrent-session limit ("I'm at my limit").
Your access was paused after repeated blocked requests. The owner restores it on Members.
The message was blocked as clearly harmful (malware, attacks on systems you don't own, jailbreak attempts, harassment). You're told so. Security work on your own systems is allowed.
A tool is down (see below). The conversation may have failed when it started; send the message again and it will start without the broken tool.
The workspace isn't active (offboarded). An owner or support can reactivate it.