this could also be a simple syntax error. I had a syntax error which threw on FF but not Chrome as follows:

    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js">
        defer
    </script>

This could also be a simple syntax error. I had a syntax error which threw on FF but not Chrome as follows:

    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js">
        defer
    </script>