Featured Content & Featured Slider not accessible after setting site to https

Dear support, I just set http://www.stiftung-meeresschutz.org to site name https://stiftung-meeresschutz.org everythings seems to have worked out so far: changed the wp-config.php changed adresses in admin worked with Better Search Replace to change URLs in database set the rewrite rule in .htacces but now I can not change anything using the customizer in the featured Content & featured Slider settings, they just don't show... guess there must be additional changes in the settings of some of the theme scripts. Do you have any idea where to look and what do do? Thanks Regards Ulrich