Reconnect drone in Ableton

What did you do with the drone before?

If it was tied to a rack (arrangement or global), it stays so. The only way to release it is to delete the rack module in Synfire, but that's probably not what you want to do.

If you say "reconnect", how was it disconnected?

Need to understand the context.

So you open your project in Ableton and Synfire and Synfire complains it can't find the original drones?

Make sure you open the Ableton Live set first, then open the Synfire arrangement.

When you save your project, always save Synfire first (don't yet close it) then save the Ableton Live set. After that's done, you can close both programs. Background: When you save a Synfire arrangement, it sends its current state to the drones. The drone's contents are then saved with the Live set.