I just drag and drop the URL of JS file inside my ASPX page
It might not work like that.
Sounds like it is
relative path issue. At times, after deployment the path referenced as a source for images, stylesheets, etc is not correctly formed. This leads to no file found at the location referred because of which images don't download or style-sheets does not get applied.
You would need to make sure that the path is correct such that file is found and used.
I would suggest you to use this Tip and resolve the path correctly before setting the source of the file:
Resolving Paths in a Multi-Folder WebSite[
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