Hi Abhishek,
I will do better than telling you what happens, I will show you as well.
Attached is a screen capture showing:
A freshly booted chromebook
I click on Enpass to start the application & enter my password
I show you the settings > autofill configuration to verify that autofill is enabled
I start Chrome
I go to discussion.enpass.io
I click the "Existing user? Sign in" link
The "Sign In" dialog appears
I click the Enpass icon
A new tab in Chrome opens saying that Enpass is "Looking for Enpass App..."
Which then changes to the "Connection Error!" message