nomovies

At the description of the plugin, it’s said:
This plugin serves as a temporary solution, enabling the migration script for your site to give your plugin and theme authors some more time to update, and test, their code.

I have maybe the same problem. My gallery do not show images.
There is a conflict with WordPress 5.5

Found this plugin Enable jQuery Migrate Helper
And now the gallery is working.
the website

With the update to WordPress 5.5, a migration tool known as jquery-migrate will no longer be enabled by default. This may lead to unexpected behaviors in some themes or plugins who run older code.

This plugin serves as a temporary solution, enabling the migration script for your site to give your plugin and theme authors some more time to update, and test, their code.