Sirat pro ipad issues

HI we are using sirat pro theme and have been told of an issue of the website not showing the hamburger mobile menu tab.

The ipad is using safari, not been told yet what model ipad or screen size.

Could this be a problem with the sirat theme not resizing or is it an ipad issue ???

The main menu bar is not showing and neither is the mobile hamburger menu.

All help gratefully recieved, many thanks in advance.

Joe