For a brief period of time today Google suffered a global outage in their load balancer offering. This impacted requests issued to the url2png beta platform directly, as well as captures against sites hosted behind Google Cloud Global Load Balancers on the general internet. At this time, no outstanding issues are noted.
For additional details see:
Google Cloud Networking Incident #18012
The issue with Google Cloud Global Load balancers returning 502s has been fully resolved.https://status.cloud.google.com/incident/cloud-networking/18012