"Timed out" indicates Stripe was able to establish a connection to your server, but it took too long for your server to provide a response. Stripe expects your server to promptly respond with an HTTP status code in the 200–299 range to indicate the Event was successfully received.
Give the following a try:
Audit your webhook processing code and make sure you return a 2xx status code quickly: If you need to perform long-running tasks after receiving an Event from Stripe you should acknowledge receipt of the Event immediately, then perform the long-running tasks afterward (many people add received Events to an internal queue for serial asynchronous processing)
Make sure your server is operating normally: Check for abnormally high CPU or memory utilization, full storage or disk space issues, and errors or warnings in server logs