Created a new article and uploaded the pictures, these are not displayed in the gallery section. Appears instead the loading icon. I don’t know if the problem is caused by WP, by the theme or by the server. I tried to disable all plugins, but nothing has changed.
I solved the problem by replacing the folder and the file functions.php functions with those of the new version of the theme, but now the site seems to have lost part of css styles that is set through the Theme Options panel.