The issue of "request timed out" when pinging the public IP address of the EC2 instance could be due to the Network ACL (NACL) inbound rules.

Check NACL Inbound Rules:

Network ACLs act at the subnet level and can explicitly allow or deny traffic to or from a subnet.

Ensure that the NACL associated with the subnet containing the EC2 instance has inbound rules that allow ICMP traffic (which is used for ping).

Example rule to allow inbound ICMP traffic:

Rule Number: 100

Type: ICMP

Protocol: 1

Port Range: N/A (ICMP doesn't use ports)

Source: 0.0.0.0/0 (or specific IP range)

Allow/Deny: ALLOW