Could you please help me with your site URL so that I can have a look at it?
Thanks for trying and testing and the suggestion. I did: Preferences > Privacy > Remove all website data. But it is still displaying the moblie layout on Safari. I'm on an iMac (21.5-inch, Late 2015), El Capitan 10.11.6. Muse CC 2017.
Interestingly, I asked my son to look at it on his iMac - it shows the desktop layout on Safari and Chrome. Weird!