something wrong ,there was an error when processing the dataset.

500 internal server error is generally related to a time out server side (the refresh took too long) especially with SharePoint connections that can be extensively long and complex.

The technical answer is that 5** errors are server side and the malfunction is beyond Power BI.

There are a significant number of old solutions that could be explored for a solution. Ultimately I would recommend trying to optimise your sharepoint connector to only bring in exactly what you need.

Credit to amitchandak from previous posts.

https://community.fabric.microsoft.com/t5/Desktop/DataSource-Error-Web-Contents-failed-to-get-data-from-500/m-p/392703

https://community.fabric.microsoft.com/t5/Desktop/DataSource-Error-Web-Contents-failed-to-get-contents-from-app/m-p/2417545

https://community.fabric.microsoft.com/t5/Power-Query/DataSource-Error-Web-Contents-failed-to-get-contents-from-URL/m-p/2181574