Hi, @Duchemin, Dominique
Thank you for posting in Microsoft Q&A forum.
This could be due to a variety of reasons such as network connectivity issues, client machine issues, or even security software blocking the query.
One thing you can try is to check the status of the clients that are not responding to the query. You can also try to run the query again and hold down the Ctrl key while clicking Run to rerun the query on the clients.
If the issue persists, you may want to check if any security software is blocking the query. As mentioned in the documentation, some security software may block scripts running from c:\windows\ccm\scriptstore which can prevent successful execution of CMPivot queries. It is recommended to exclude %windir%\CCM\ScriptStore so that the anti-malware software permits those features to run without interference.
The reference:
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