Menu does not show on mobile

Hi! I have a problem with my site.

Yesterday I made a few changes on my site and today I noticed that the main menu isn‘t showing up on mobile devices. I searched a lot on WP Forums and found out that the menu does show if I remove ?Menu1“ as main menu and do not define a menu. In this case (without a menu defined) it does show the menu on mobile devices. But for sure if the menu is not defined it does show every single page in the dropdown menu and thats not what I want. I don‘t understand how this happened. Can anyone help? Thanks!

Theme I am using: Mesmerize (free version)

Some plugins I am using (could one of these trigger the problem?) :
– Disable Comments by Samir Shah
– Jetpack by Automattic
– Mesmerize Companion
– NextGEN Gallery
– UpdraftPlus
– WooCommerce Germanized
– WP Fastest Cache by Emre Vona
– WP Meta and Date Remover by Presad Kirpekar
–

The page I need help with: [log in to see the link]