ERPNext site works on some networks but not accessible on others

Hello Everyone !
I am facing an issue where our ERPNext site works properly on some networks (office Wi-Fi, certain ISPs) but is **not accessible on other networks.

What is the issues ? please suggest to me resolve this issues.**

fail2ban

Thanks for your reply.
Could you please explain how Fail2Ban might cause this issue?
Which jail/logs should I check, and how can I confirm if some networks’ IPs are being blocked?
But It blocks for only 10 to 30 minutes only , Not more than 30 min.

First step - can you ping the site from the other networks
If so do a curl mysite.com

Maybe a routing issue or interface on wrong network. Must provide at least a logical infrastructure to help.