Hi there!
Thanks for your query.
I have visited the link: campenmithund.ch and offcanvas is showing there at my end.
Could not find this one: neu.marty-immovision
For this site: waldvogel-wila.ch kindly use the following code in your custom CSS:
#sp-header #offcanvas-toggler.offcanvas, #sp-header #offcanvas-toggler.mega {
display: block !important;
}
#sp-header nav.sp-megamenu-wrapper #offcanvas-toggler {
display: none !important;
}
.burger-icon>span {
background-color: black;
}
Note: Path towards custom CSS(Joomla 3): Extensions>Templates>Styles> Click on your current default template name then choose Template Options. Then find custom CSS within the custom code.
Best Regards