The response above was not helpful as I did use ChatGPT to debug and the issue was not about errors in the code or not closing the bracket.
Found the solution -
For the font code, use this:
@font-face {
font-family: 'Jost';
src: url('https://static1.squarespace.com/static/627b2b8d29670e0040a5311f/t/6530c8f1a2891e484b1cad0f/1697695985126/Jost-SemiBold.ttf')
}
.header * {
font-family: 'Jost' !important
}
For the sticky header, grab the section ID and make the whole section sticky instead of just a block within a section.