Creating a custom directory header

I recently released an app for which I used the ionic framework and have just started another one but a problem arose and I believe it might be due to a functional change that I am not aware of.

I am creating my selector: ‘app-header’ in a Directive inside my Header class which I would like to be reusing in other places.

When I insert the tag to another .ts file though, I get an app-header not known element error.

Does anyone know why that is and how to avoid it?

Thanks :slight_smile: