Website doesn't work on mobile

Hi,
I just got a message from a customer saying that she couldn’t view my website on her mobile phone, so I tried on my own and I can see that it says that “this website is not available” when I try to access it. Do you know what might be wrong? It looks good on my computer, so it’s only on the mobile it’s not working.
Kind regards,
Johanna Klawitter Beusch
P.S. I uploaded the latest version of WordPress yesterday. I don’t know if it might have something to do with that??