Why am I getting 404 – Page Not Found error after uninstalling the app?

Uninstalled the Under Construction app, but the page still exists or displays a 404 error. How can I fix this?
First of all, don’t panic whenever you face this error on your website.
Go to Online Store > Themes, and go to “Edit code“.
The residual code may be found in “theme.liquid” before tag – {% include ‘under-construction’ %}
Once this code is removed, the coming soon page and the error should no longer appear.

For a quick view of the edit template, check the below image

Why I'm getting 404 - Page Not Found error after uninstalling the app?