Unable to Access Website from Smartphone

Hi Everyone,

I’m currently using the Smartline Lite theme. I can access the website from my computer and tablet. However, I’m unable to access the site using my smartphone.

My website is https://www.mattere.com

I would appreciate any assistance or explanation in layman terms. Thank you.

PS: My hunch tells me that this may need a stylesheet.css modification but I don’t know where to start, what to look for and what code to put in.