Hi there,
you have this CSS which is affecting the width of the main content across the entire site:
@media only screen and (min-width: 769px) {
#primary {
max-width: calc(100% - 300px);
}
#right-sidebar {
min-width: 300px;
}
}
If you need that CSS still, change it to this, it will only apply to pages where the right-sidebar is enabled:
@media only screen and (min-width: 769px) {
.right-sidebar #primary {
max-width: calc(100% - 300px);
}
.right-sidebar #right-sidebar {
min-width: 300px;
}
}