did you try enabling WORDPRESS debug (like so https://docs.wp-pizza.com/troubleshooting/)
and / or disabling any/all other plugins ?

what’s really happening is simply that that loading screen does not get removed – the debug settings in the plugin do bypass that “cover” so to speak to be able to see what’s happening , so it’s not a case of it working so to speak when you enable debug . it’s working with or without , but that covering spinner does get get removed because some script somewhere does not finish it’s job
so disabling everything else is the first step to narrow this down

i dont think that plugin is the problem itself, as installing it here and using it with the default settings works just fine

in fact, looking at your site at https://www.soledipizza.it you still seem to have that plugin running i cannot see any issue

..?!