Hello,

Sorry to say but the Mobile Menu does not support mega menu blocks as there is no space enough for mega blocks. Thus, it is necessary to create a clone of the Main menu without mega menu blocks and assign it as the Mobile Menu in Appearance > Menu. The mobile menu may be multi-leveled.

You can read more about it here on the following Documentation Guide:
https://xtemos.com/docs-topic/adding-menu-to-the-site/

In this above link, skip directly to the Mobile Menu heading for its related guide.

Best Regards