The Theme Designer App will close in February 2020 when stores using it will no longer see the styling changes provided by the app.
From January 2020, you may see "expired" button images on your storefront if it continues to use the Theme Designer app or CSS provided by the older Theme and Tweak services. The "expired" images look similar to this example:
If you are seeing images similar to these on your store, you need to take action, as these images will be removed in March 2020.
What you need to do:
If you have issues implementing the steps above, it may be possible to provide a new Ecwid Custom CSS theme for your storefront that provides the same styling but without using e-shop designer services. If you need this, please contact email@example.com giving your Ecwid store id. If you would like me to apply the changes necessary, I can do that for you if you provide your Ecwid user and password.
Ecwid now has many options for styling your store that were not available when e-shop designer was first created.
Check out this Ecwid help.
And, more specifically this article.
Also, you can try the Decorator app which a more recent offering from e-shop designer.
Theme Designer app, Themes and Tweak are no longer available but the new Decorator app is recommended if you want to easily style your storefront.