Ok the CSS above it ie. this is missing a closing }
so your author box styles are only being applied to larger screens. In the CSS below i have commented where you need to add the missing bracket.
@media (min-width: 769px) {
#right-sidebar {
width: 350px;
}
.inside-right-sidebar {
padding-right: 20px;
}
body:not(.no-sidebar) #primary {
width: calc(100% - 350px);
}
} /* Add this bracket */