Share button disappeared

Hello everyone!

I have a question for you. I run a website about sewing stuff. When I open my site on the computer there is a share button as a sidebar on the left side of the screen. But when I open it on my phone in Safari there is no share button at all. Do you know how it can be fixed?

Anyway, thank you.

Here is a link to my site, if you see the cause of this error.