network load balncer

This troubleshooting document might be of help.

For example, a connection might timeout if 172.25.1.73 is as well the target of your NLB (172.25.5.235), and if the IP preservation is enabled, which is so-called hairpinning mentioned in this paragraph.

Meanwhile, consider adding -v to the curl command so you get to know more details for further troubleshooting.

To confirm, you are accessing your EC2's and not an NLB as you mention private server IP?

Ensure your security groups allows access from your IP to port 80