If the AI answers without citing a source, it is not retrieving from your KB. Three causes.
1. Grounding turned off for this channel
Check Settings > AI > Grounding. Make sure the channel (chat, email, phone) has at least one source toggled on.
2. KB is empty or in Draft
The AI grounds against Published articles. Check Settings > Knowledge base. If everything is Draft, hit Publish on the ones that are ready.
3. Retrieval threshold too high
Settings > AI > Retrieval. The similarity threshold defaults to 0.65. If your KB is small, drop it to 0.5 so more articles match. Trade-off is more loose grounding, but better than no grounding.