Blog filtering with advanced code help

I am trying to migrate https://www.tablerock.church/sermons  from 7.0 to 7.1 

In 7.0, there is a code used in header code injection for dropdown filter (you can see the dropdown in this page https://www.tablerock.church/sermons ) which is stated below:

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<script>

function getQueryVariable(variable)
  {
         var query = window.location.search.substring(1);
         var vars = query.split("&");
         for (var i=0;i<vars.length;i++) {
                 var pair = vars[i].split("=");
                 if(pair[0] == variable){return pair[1];}
         }
         return(false);
  }

  if( $('#collection-5c9e4b1553450a6213e3a5a7 .Main--blog-list').length == true ) {

    var postHTML = [];
    var categories = [];
    var tags = [];
    var preacherIds = [];
    var preachers = [
      {
        'name' : 'Andrew Knight', 
        'id' : '5d2515a11dfbb500011c1cf4'
      },      
      {
        'name' : 'Don Straka', 
        'id' : '5cb4faab25a88200014f192b'
      },
      {
        'name' : 'Luke Miller', 
        'id' : '5d2515ad4ffbbe00012e4ca6'
      },
      {
        'name' : 'Luke Salik', 
        'id' : '5d251581b06cd600016393ad'
      },
      {
        'name' : 'Ryan Eagy',
        'id' : '598c964b59cc689d94d32c00'
      }
    ];
    
    
    var books = ['Genesis','Exodus','Leviticus','Numbers','Deuteronomy','Joshua','Judges','Ruth','1 Samuel','2 Samuel','1 Kings','2 Kings','1 Chronicles','2 Chronicles','Ezra','Nehemiah','Job','Psalms','Proverbs','Ecclesiastes','Song of Solomon','Isaiah','Jeremiah','Lamentations','Ezekiel','Daniel','Hosea','Joel','Amos','Obadiah','Jonah','Micah','Nahum','Habakkuk','Zephaniah','Haggai','Zechariah','Malachi','Matthew','Mark','Luke','John','Acts','Romans','1 Corinthians','2 Corinthians','Galatians','Ephesians','Philippians','Colossians','1 Thessalonians','2 Thessalonians', '1 Timothy','2 Timothy','Titus','Philemon','Hebrews','James','1 Peter','2 Peter','1 John','2 John','3 John','Jude','Revelation'];

    var xhrPosts = new XMLHttpRequest();
    xhrPosts.onreadystatechange = function() {
        if (this.readyState == 4 && this.status == 200) {

           if (this.responseText[0] === "<") {
             var start = this.responseText.indexOf("[{");
             postHTML = JSON.parse(this.responseText.substr(start));
           } else {
             postHTML = JSON.parse(this.responseText);
           }

           categories = postHTML.collection.categories.sort();
           tags = postHTML.collection.tags.sort();

           var dropDownItemsCategories = '';
           var dropDownItemsTags = '';
           var dropDownItemsBooks = '';
           var dropDownItemsPreachers = '';

           // Create Category Select Options
           for (var i = 0; i < categories.length; ++i) {
               dropDownItemsCategories = dropDownItemsCategories.concat('<option value="'+categories[i]+'">'+categories[i]+'</option>');
           }
           // Create Preachers Select Options
           for (var i = 0; i< preachers.length; ++i) {
               dropDownItemsPreachers = dropDownItemsPreachers.concat('<option value="'+preachers[i].id+'">'+preachers[i].name+'</option>');
               preacherIds.push(preachers[i].id);
           }
           //Create Topic Select Options
           for (var i = 0; i < tags.length; ++i) {
             if ( !(books.includes(tags[i])) ) {
               dropDownItemsTags = dropDownItemsTags.concat('<option value="'+tags[i]+'">'+tags[i]+'</option>');
             }               
           }
           // Create Book Select Options
           for (var i = 0; i < books.length; ++i) {
             if ( tags.includes(books[i]) ) {
               dropDownItemsBooks = dropDownItemsBooks.concat('<option value="'+books[i]+'">'+books[i]+'</option>');              
             }
           }
           
           var dropdown = '<div class="category-select-block" style="margin-bottom:28px;text-align:right;"><div class="style-wrap-arrow"><select class="category-select" style="max-width:100%;"><option selected="selected" disabled="disabled">Filter sermons by</option><optgroup label="Sermon Series:"><option value="All Sermons">All Sermons</option>'+dropDownItemsCategories+'</optgroup><optgroup label="Preachers:">'+dropDownItemsPreachers+'</optgroup><optgroup label="Books:">'+dropDownItemsBooks+'</optgroup><optgroup label="Topics:">'+dropDownItemsTags+'</optgroup></select></div></div>';
           $('.Main-content').prepend(dropdown);

           if (getQueryVariable('category')) {
              $('.category-select option[value="'+decodeURI(getQueryVariable('category'))+'"]').attr('selected','selected');
           } else if (getQueryVariable('tag')) {
              $('.category-select option[value="'+decodeURI(getQueryVariable('tag'))+'"]').attr('selected','selected');
           } else if (getQueryVariable('author')) {
              $('.category-select option[value="'+decodeURI(getQueryVariable('author'))+'"]').attr('selected','selected');
           }

           $('.category-select').change(function(){
              if(this.value !== 'All Sermons' && categories.includes(this.value) ) {
                  window.location.href = location.protocol+'//'+location.host+location.pathname+'?category='+encodeURI(this.value);
              } else if(this.value !== 'All Sermons' && tags.includes(this.value) ) {
                  window.location.href = location.protocol+'//'+location.host+location.pathname+'?tag='+encodeURI(this.value);
              } else if(this.value !== 'All Sermons' && preacherIds.includes(this.value) ) {
                  window.location.href = location.protocol+'//'+location.host+location.pathname+'?author='+encodeURI(this.value);
              } else {
                  window.location.href = location.protocol+'//'+location.host+location.pathname;
              }
              
           });
        }
    };
    xhrPosts.open("GET", location.protocol+'//'+location.host+location.pathname+"/?format=json-pretty", true);
    xhrPosts.send();

  }
  
});
</script>

It is not working on 7.1 blog page. The 7. 1 website link 

https://springtail-nonagon-dchs.squarespace.com/sermons

password:  tablerock

Anyone can assist on this please? Thank you in advance!