Doesn’t show up with theme

I have an issue using the Plugin. It worked on my local test environment (with the standard theme) but it is not showing on the website where I want to use it.
On this website I am using the theme ?TheGem“ (https://themeforest.net/item/thegem-creative-multipurpose-highperformance-wordpress-theme/16061685?gclid=EAIaIQobChMIxZ2Iv-6g8QIVDgOLCh3ezgXdEAAYASAAEgJ1BfD_BwE). I think this is the reason why it doesn’t work.

Does anyone know if there is a possible way to use both – the plugin and the theme?

PS: Sadly I am not able to link the website, because it is password protected and not supposed to be public yet.