Page not loading correct page template

I have looked everywhere regarding documentation on this issue and cannot find anything.

I have just made a custom theme and am currently unable to change to a new template, or revert to the default template.

I have tried clearing cache and clearing browswers but to no avail.

Is there are file in the the wordpress setup that allows you to manually change which page template a specific page points to?

Here is the example my Icons page, https://www.fine-art-icons.com/icons/ should be the same template as https://www.fine-art-icons.com/view-icons/

Hope someone can help. Let me know if further information is needed.