Simple custom code suddenly doesn't work across multiple sites (logo swaps)

I have been using this code for ages with no issues: 

<script>
  window.onload = function() {
    document.getElementsByClassName('Header-branding-logo')[0].src = 'https://static1.squarespace.com/static/6206bdb5ff4ac21c6a8eda7f/t/6271f361756bbb4fe37cd2f5/1651635041619/clevelandDx-dark.svg';
  };
</script>

It just stopped working across multiple sites that i have built and manage. It's a simple way for me to swap the logo instance from a 'solid white' to 'full color' for specific pages. 

The file still loads properly if you enter the path in a browser. Also - - - the file format has no bearing. PNG files on other sites using the same code to implement seem to also not work. 

Thanks!

BRINE, SS v 7.0

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