I verified AS2's routing table and firewall rules, performed a traceroute from AS2 to 8.8.8.8, and coordinated with AS1 to refresh their ARP entries and confirm their routing table. After re-verifying AS2's configurations, I communicated with AS1 to suggest investigating upstream connections. We agreed to jointly escalate the issue to higher-level support for further investigation, as both AS2 and AS1 had confirmed their configurations were correct.