It is a fairly popular problem because there are some stores still using the liquid themes. This kind of theme does not support to add Reelfy section/block in the theme customizer. Hence, you must find another way to publish your gallery.
First, you need to enable the Reelfy app scripts.
Then, please find and add a custom liquid section to the template.
In the next step, you need to copy the embed code of the gallery and paste into that custom liquid section.
Click Save and you are done!
If you cannot find Custom Liquid in the section list, please refer to create Custom Liquid section in Shopify
