It seems that you have customize the code. So the navigation menu is not displaying while viewing in smaller device. We cannot guarantee our themes will function with all 3rd party components and plugins. You need to hire a developer to fix this issue, if you want to use custom MLS software in your theme.
Once you remove the code that you have installed in theme and check whether the same problem persuits or not. If not then deactivate all the plugins one by one that you have installed in your dashboard. There may be some jquery conflict so that you are getting this issue. You may check it in our demo site that its working fine.
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