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My Agent Stack isn't replying — where do I look?

When an Agent Stack stops replying or never replies in the first place, work through these checks in order — channel wiring, stack enabled, specialist enabled, capabilities failing silently.

Updated May 13, 20264 min read

My Agent Stack isn’t replying — where do I look?

A stack that’s not replying is usually one of five problems. Walk through them in order — most teams find the cause by step three.

1. Is the stack wired to the channel?

A stack only handles conversations on channels you’ve connected to it. The most common cause of “the stack isn’t replying” is “the channel doesn’t know about the stack.”

Open your channel’s settings (e.g. Settings → Web Chat, Settings → Email, Settings → Voice).
Look for an “AI agent” or “Agent stack” field. Confirm it points at this stack.
If it’s empty or points at the wrong stack, set it correctly and save.

2. Is the stack enabled?

Open Settings → Agent Stacks → [stack] → General.
Confirm the Enabled switch in the header is on.
If it’s off, toggle it on. New conversations on the stack’s channels will start being handled.

3. Is the relevant specialist enabled?

The stack might be on, but the specialist that should answer might be off.

Open Orchestrator tab.
Click the specialist node that should handle the topic.
On the Setup sub-tab, confirm the specialist’s enabled toggle is on. (Disabled specialists show a “Disabled” badge on their canvas card.)

4. Did a capability fail silently?

When a specialist is configured to call a capability and the capability errors, the AI may go silent rather than reply with an error message. The fix path:

Open the conversation in Conversations (or in Monitor for in-progress).
Look for capability execution traces or error notes in the conversation timeline.
Open the offending capability in Settings → Capabilities and check its execution log.
Common causes: API key expired, target endpoint changed, response format changed.

5. Is handover blocking the AI?

If handover triggered earlier in the conversation, the orchestrator state may be human_active — meaning the AI is no longer replying because a human took over. Confirm:

The conversation should appear in your team queue, not in the Alia tab.
If you expected the AI to keep replying, that’s a bug in the handover trigger configuration. Review Handover → Triggers and Delivery.

Less common causes

Routing rules in the orchestrator config send every message to a specialist that doesn’t exist. If a rule says “always route to Old Specialist” and Old Specialist was deleted, the router falls through to the catch-all (or fails entirely). Open the Orchestrator slide-out and audit your rules.
No specialist at all. A stack with zero specialists has nothing to route to. The Orchestrator canvas shows the empty state in this case.
Channel disabled at the tenant level. Even if the stack is wired correctly, the channel may be disabled. Check the channel’s settings page.
API key / Anthropic outage. Rarely, but the AI service can be temporarily unavailable. Check the Sidekick badge for any health indicator, or your status dashboard if your tenant has one.

When in doubt — use the Testing tab

If you can reproduce the silence in the Testing tab, the problem is in the stack (specialists, knowledge, capabilities). If the Testing tab works fine but production is silent, the problem is in the channel wiring or routing.