Museo Slab CSS for H3 and H4 not working on Safari

Site URL: https://www.takecontrolphysicaltherapy.com/

Hi, I have added a secondary font for my H3 and H4 headers on my client's site, but it won't load properly on Safari (desktop or mobile). The font is a Squarespace available font (Museo Slab). Here is the code I am using: 

/* header changes */
h3 {

    font-family: "museo slab"!important; 
    font-weight: 500;
    line-height: 1.15em;

}
h4 {

    font-family: "museo slab"!important; 
    font-weight: 500;
    line-height: 1.15em;

}

TIA! 

Try change code to this

h3 {
    font-weight: 500;
    line-height: 1.15em;
    font-family: 'Museo Slab', sans-serif !important;
}