Hi , @Anonymous
This error code means that your "@triggerBody()?['entity']?['Power BI values']" return null in your side.
This may happen when the button do not get the data from your Power BI side.
You need to check:
(1) You need to pass the data in Power BI side.

(2)You need to trigger this flow only in Power BI!
(3) You can check if you get the data successfully in your flow run history:

If you do not get the data , you can re-create your flow in Power Bi side to test again.
Best Regards,
Yueyun Zhang