When I take a look at the screenshot you provided, I can see that the template for the page you are creating is certainly a custom template and not a native Shopify one:
It looks like it may be a code template from the third-party app Pagefly, in which case you could reach out to the app developers directly to ask for help removing the residual code.
Alternatively, if you click on this, can you see alternate templates available in a drop-down? If so, can you test them out to see if any of them work? If any of the other templates work, you could simply opt to change the template suffix every time you build a page to make sure it is not using the Pagefly template that has been left behind by the app.
I hope this helps, let me know if you have any other questions!