Php script with ajax calls (every 4 seconds) stops working after few seconds

I have created a web system for my client for taking orders in his restaurant. The system works fine in a vps. I moved the system to GoDaddy basic Plan(it is used by maximum of 3-4 PCs at a time). There is page where I do ajax call in the background for every 4 seconds to Synchronize the data in the other PCs where the same page is opened (The page where all the orders are listed/added/updated). When I open this page GoDaddy serever It loads and after 50-60 seconds, ajax calls fail and if I reload the page now, it says

This page isn’t working xxxxxxxxxxxxx.com didn’t send any data. ERR_EMPTY_RESPONSE

please someone help me fix this