that site is using a Divi Template which is replacing the entire theme template, which includes all the hooks the theme uses to insert things such as the Off Canvas Panel. Is it possible to change the template back to default ?
I can see that – but on your old site it is using the default theme template and the content. Whereas on the broken site the theme template has been replaced with a Divi Template. I am not a user of Divi – i would assume there is a setting somewhere to use the default theme?