It appears that on your Plone website, the data-widget-id attribute is missing from the embed code (<a class=“twitter-timeline” …>.)
If your CMS is stripping the embed code out, you can try changing the embed code like this. Where the original embed code looks like this:
Tweets over “@amecboard”
Change it to this, with the widget ID as a camelCased query-string parameter instead:
Tweets over “@amecboard”
Ben