Megamenu sub menus dont work

Hi

I have installed megamenu just fine and the sub menus work but whenever I install another extension of yours on the same page the sub menus don't work anymore.

Running joomla 3.4 latest

Have tried with other extensions and the same thing happens

Help please

Dear ponygirl!
Thank you for using product our.
Please send information of website via private messages. I will check it for you.
Best Reagrds,
Huyen Tran