Mobile Navigation not Working

WP Theme – Kiyono

Am doing a website rebuild, all going swimmingly until I checked mobile, the hamburger menu though visible isn’t working. Have try to solve it but am running out of ideas.

What I’ve tried;

– Cache deleted.
– Deactivating all plugins, still no response.
– Tried adding a Mobile Menu plugin that just complicated things (actually the whole site-header went white).
– Deleting an additional CSS code I used for sticky header, still nothing
– Making sure all my font colours <p> – <h6> were dark, this did nothing.

Can’t think of anything else to try, maybe it might be the theme itself?? am baffled so am putting out to the forum to see if I’m missing anything.