need some help to resolve my menu issue on mobile devices

I have an issue with the way my site displays its mobile menu.
It should look like this -
Currently it looks like this -

When the page loads it appears for split second then disappears so i think its just a matter of ensuring the buttons are brought to the front and the background send to back if possible? or might be be something else if i could please get some help?

Domain -
support access is open

Please don't post any brand related information/ screenshots or domain links as i have had issues with google caching this information and linking it to their google searches of my site ... very bad for brand... please use temporary image upload / tiny url / pastebin etc to mask this information.