The script tag should have this pattern
<script src="https://cdn.usefathom.com/script.js" data-site="XXXXXXXX" defer></script>
but is currently
<script src="https://cdn.usefathom.com/script.js" data-site="XXXXXXXX" defer=""></script>
See https://www.w3schools.com/tags/att_script_defer.asp
Small change to the script attribute.
Fixed
3.0
Code