ERPNext on AWS server disconnectng frequently
This is due to fail2ban which is treating no.of requests from a LAN connection as bruteforce attack and hence blocking the further requests. After purging fail2ban everything worked fine.
We have an ERPNext open software which is working fine on AWS Large Instance of 500 GB HDD. Recently, as it is an excess configuration for our usage, we downgraded to Medium Instance and 20 GB HDD. Also, we have changed the OS, from Ubuntu 14.x to 16.x. So the python version also got changed(i.e., Python 2.7.6 to Python 2.7.12). From then, we are facing a frequent disconnecting issue i.e., it shows site not found when we access the site. We are using Elastic IP. We upgraded to a Large instance and the same issue still continuous. So it is not an instance issue. 
I feel this is weird because, when few people at my office, says it is not working, I can access the site from my home at the same point of the time. But, they are able to access other sites, except this ERP site.
I'm not getting what caused the problem. Can anyone help me with this? Is this a problem with AWS or IP issues or Ubuntu 16.04 not supporting ERPNext or Python Version? I've left with no clue. Any help is greatly appreciated. Thanks.