I have made the AMP page for my website following the Google docs. Then I performed its validation and everything is fine in there as well. I have linked the AMP and non-AMP pages too as follow:
Non-AMP page:
<link rel="amphtml" href="https://www.example.com/url/to/amp/document.html">
AMP page:
<link rel="canonical" href="https://www.example.com/url/to/full/document.html">
And finally, I'm getting the AMP version in Google Search in my mobile. But in some of the mobile phones it's not working as expected. It's not showing the AMP version in the search result.
In my website:
The URL to the home page is: https://www.example.com/
The URL to the AMP page is: https://www.example.com/amp/
Is this problem due to the cache issue of the mobile or depends upon the mobile or due to the AMP indexing issue? Or is it due to the URL issue? Does it depend upon the URL like https://www.example.com/?amp and not https://www.example.com/amp?
PS: In most of the mobile it worked. In some it didn't. The site URL mentioned above is just the example.