CSS Button effects not working across browsers

Having a few issues with a CSS Button effects not working across browsers.

It displays as I would like it in Chrome, but not Firefox.

Can't seem to find the root of the problem. Here is what I have.

Fiddle

<a class="soft">Button</a>
Code (markup):

a.soft {display: inline-block;font-family:'Varela Round', sans-serif;padding:2rem3rem;font-size:1.25vw;box-shadow:-10px-10px20px0#E6E6E6,10px10px20px0#ABABAB, inset 10px10px20px0#E6E6E6, inset...
Code (CSS):

CSS Button effects not working across browsers