AMP Redirect not functional

Are you using any caching plugins? if so, then you have to enable the mobile caching support as well. Here’s a tutorial which helps you to find that option with some popular caching plugin. https://ampforwp.com/tutorials/article/how-to-redirect-all-mobile-visitors-to-amp/#here-is-the-list-of-cache-plugin-which-supports-the-mobile-redirection