If you can’t load the WP Mobile Menu in HTTPS this probably means that something is wrong in your HTTPS Settings.

Go to the WordPress General Settings (Settings-> General) and double check that the two URL’s are using the HTTPS protocol.

Something like the screenshot below where https is used in both URL’s.

If your HTTPS settings are similar and you still can’t load WP Mobile Menu, we would suggest that you install the following plugin called Really Simple SSL

Really Simple Security – Simple and Performant Security (formerly Really Simple SSL)