Background image for button – can't get it to work

Hi,
I’ve tried this (https://kriesi.at/documentation/enfold/button/#toggle-id-22) and a couple other posts I’ve seen, but nothing is working for me – I’m sure it’s user error. I’m trying to get a background image for the button in the center widget in the footer on this site (https://friendsoftheorlandova.org/) – it should be just below the Donate button. I’m using the custom color attribute – I tried leaving that blank, using the default, etc. – nothing worked. I have the custom class set and in my CSS – any ideas?

Thanks!