Plugin Upgrade Notice is not Working

I have added upgrade notice in plugin’s readme.txt and also added it’s code that is fetching upgrade notice from readme.txt.

I have tested the scenario by changing the version of plugin locally and it’s showing upgrade notice to me that is from current available release on WP repository.

When I have made live my plugin release then plugin users are not getting upgrade notice.

Anyone can tell me what could be the possibilities for this issue. Any help will be greatly appreciated.

Thanks!