By my tests, I cannot reproduce your issue in my site.
It maybe a temporary issue. Please try to "Edit Report", then re-save it on Power BI Service to see if the visuals can be pinned to dashboard properly.
You also could re-create the card visual in Power BI Desktop and republish it to check if visual can be pinned to dashboard successfully?
If you still have this issue, could you share a dummy pbix file which can reproduce the issue, so that we can help further investigate on it? You can upload it to OneDrive or Dropbox and post the link here. Do mask sensitive data before uploading.)
Community Support Team _ Cherry Gao If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.