Plugin active but not showing in source code

I installed the plugin on my WordPress site and added the container snippet, but when I view the source code on my site, it doesn’t show that the plugin is on the site at all.

I’m not sure if maybe there’s a different plugin that’s conflicting with GTM or what’s going on.. please help!

https://www.ads-software.com/plugins/duracelltomi-google-tag-manager/