External scripts no longer working

Hi there

I use a plugin to add an autosuggest component to my mocked up checkout page. Up until now it has been working perfectly, but in the last week or so I’ve noticed it’s broken even though I haven’t updated it. I use the Plugin feature to add the following code between the head tags, but have noticed it seems to break the page - the page size is ignored etc.
<script src="https://assets.what3words.com/sdk/v3.1/what3words.js?key=KXI5RKU7"></script>

https://ch6dme.axshare.com/#id=qddcp1&p=page_1

Any ideas? Thanks