API error on POST /webhooks: {"errors":[{"message":"ETIMEOUT: Asana was unable to connect to your webhook within the timeout of 10000 ms.","help":"..."}]}. No handshake request received on server logs, despite local ngrok working.

Asana's webhook creation triggers a synchronous "handshake" POST to the target URL (with X-Hook-Secret header, empty body) that must be acknowledged immediately (<10s timeout) with 200/204 + echoed X-Hook-Secret header while the create API call waits. Server connectivity issues (firewall, TLS), slow responses, or incorrect handshake handling cause connection timeout (ETIMEOUT).