Nothing you can do. As of the time I am writing this, 4 of the first 15 threads in this forum are about stock or currency data not updating. It has been an ongoing issue.
You can provide a bug report to Apple via the menu item Numbers/Provide Numbers Feedback but I don't know what they can do about it either other than try to put pressure on Yahoo Finance. Yahoo Finance provides the data.
It was suggested by another user to use Google Sheets to collect the data and then copy/paste it into Numbers. Or just use Google Sheets to do it all.