The URL may not be in the dataset as the error message explains.
If you enter the URL in PageSpeed Insights it can show whether there is "real user" data (from CrUX) or not, which will narrow it down to whether this is a Connector error or just that the URL is not in CrUX.
If if is showing fine in there, and you can share the URL (privately to me if you prefer), I may also be able to explain more,