Can’t get channel embed to work

Hi – I’ve just switched to using this plugin and have embedded single youtube videos no problem.. whenever I try to embed a channel I get the message:

Sorry, that does not seem to be a link to an existing video. Please confirm that the link works in your browser, and that the owner of the video allowed embed sharing permissions (otherwise, contact the owner of the video to allow embedding). Then copy that full link in your address bar to paste here. If you are sure your link is correct, then (1) your API key may be too restrictive (check here) or (2) you have reached your Google quota (check here). You can apply to Google for a quota increase here.

AFAIK I have the API set up correctly.. when i look at the metrics within the API account i can see that it’s throwing a 403 for each attempt to set up the channel embed.. but i can’t see any more details than that

channel I am trying to embed:
https://www.youtube.com/channel/UC43mYWML5nKIL-uPPDYersA

can you assist please? Is this a permission issue with the youtube account or an error setting up the API?

thanks in advance.
dave