Hi Ashok P,
To better assist you, can you please provide more information to your issue?
Is it only a specific feature layer, or every feature layer. Are you clicking it via web map, a built-in web application or a custom application (e.g. using ArcGIS JS API)? Are you able to consistently reproduce it? Does this happen when you create a new web map with the same layer? Does this behaviour happen on another machine?
Hi Ashok P
Have a look at the events bound to the application.
Using developer's console on your internet browser (usually F12), locate the onclick event, and add a breakpoint.
Stepping through the functions would give you a clearer picture as to what might be suppressing the popup.
If you are using ArcGIS 4.x JS API,
Check to see if the autoCloseEnabled is set to true. When this is set to true, popups will close when the View camera or Viewpoint changes.