@roghithsam please send a screenshot and confirm if you are trying on normal WP installation or network enabled?
Kindly provide a screenshot for comparison that how main menu looks and appear before activating inbox plugin so i can actually trace the problem.
There is a button on your keyboad “Print Screen”, take a screenshot and save file through paint or any other image editor. Upload it to https://prnt.sc/
Alternatively:
Deactivate inbox plugin and let me know, i will check your website again and your main menu will be appearing.
@roghithsam thank you, please wait and i will come back with a solution.
I have checked both versions, one with activated plugin and other when plugin is deactivated.
Your theme is using a few classes which are being exploited by bootstrap CSS.
One those classes is “dropdown-menu”.
There are two solutions:
1) You manage to change class names within your theme.
2) I can provide an option to optionally turn boostrap OFF in inbox. But it will leave the plugin totally disturbed as without CSS.