It is an error in which you are referencing something that doesn’t exist.

I recommend re-remixing the page you want to remix. If you click ‘edit’, the HTML editor on the bottom right doesn’t seem to match the HTML of the original generator, which is why it is throwing an error that it cannot find the thing that it is supposed to output, the title.

An error has occurred somewhere in your code (in lists or HTML): The expression ‘[title]’ returned nothing (undefined). You may be trying to reference a list, variable, or function that doesn’t exist. Here are some common causes of this error:

You tried to reference a list/variable that you haven't created. For example, if you wrote [animal], but there was no top-level list called "animal", then you would get this error. Note that names are case-sensitive - check your capitalization.
If you misspell a property/function name, then you'll get this error. For example "[noun.pluralFormm]" would produce this error because "pluralForm" has been misspelled.
If you try to access a property of an object that doesn't exist, or that evaluates to something which doesn't exist, then you'll get this error.

These errors can sometimes be hard to debug, so after you’ve given it your best shot, please post a question over on the perchance community and a friendly community member will help you out :) An error has occurred somewhere in your code (in lists or HTML): The expression ‘[output]’ returned nothing (undefined). You may be trying to reference a list, variable, or function that doesn’t exist. Here are some common causes of this error:

You tried to reference a list/variable that you haven't created. For example, if you wrote [animal], but there was no top-level list called "animal", then you would get this error. Note that names are case-sensitive - check your capitalization.
If you misspell a property/function name, then you'll get this error. For example "[noun.pluralFormm]" would produce this error because "pluralForm" has been misspelled.
If you try to access a property of an object that doesn't exist, or that evaluates to something which doesn't exist, then you'll get this error.

These errors can sometimes be hard to debug, so after you’ve given it your best shot, please post a question over on the perchance community and a friendly community member will help you out :)

If you click on the red error box, it’ll give you some clues.

The expression '[title]' returned nothing (undefined)

So you’re trying to show something called “title” but that is undefined. Looking at your list, you have nothing called “title”. Only thing within other objects (eg. page, $meta) called title. So maybe use one of those.

To use a property within an object use object.property. So for the page one, that would be [page.title] for the $meta one that would be [$meta.title].