Embedding 'content field invalid'

[CJH]

In my v1.6.0.6 site I have a calendar embedded in a page - it's one of the free calendars by Time.ly (it's quite good, works perfectly; other offerings are similar from the likes of Tockify). To get it into a cms page, you just paste in the supplied code. Example follows (with xxxxx replacing the actual link)

<script src="//dashboard.time.ly/js/embed.js" data-src="https://events.time.ly/XXXXXX" data-max-height="0" id="timely_script" class="timely-script"></script>

I have a new 1.7.4.4 site that I am developing and assumed I could paste the code into a page on the new site and continue using it. But Prestashop reports, as soon as the page is saved, that

'The content field is invalid'

The same happens with other similar calendars. Is there a setting that can allow this code to run? How to get it to work? I tried turning off the html purifier but that made no difference. Fine on 1.6, no good on 1.7.

Edited January 14, 2019 by CJH
incorrect paste (see edit history)