Unable to delete the data source with the error indicates that there is already mapping or matching via ‘Unify’.
Follow these steps:
1.Select the entities you would like to edit or remove via ‘Select’.
2.After unticking required entities, save changes and proceed to delete the data source via ‘Data Sources’ on the left-hand navigation bar under ‘Data’.
Note that you cannot untick entities that have already been matched.
Steps for deleting a "Matched" Data Source:
Note you can delete entities that are not the Primary or Secondary entity/ data source on the Match order. See the example below.
If you need to delete the Primary or Secondary entity / data source, you will need to reset your environment by selecting the ‘Settings’ on the top right-hand corner.
And selecting ‘Delete’ on the ellipse of the applicable Environment.
This will trigger a prompt advising you that this will remove all data and to type in the Environment name as precaution that you don’t accidentally delete all your data.
Once done you can setup a new Environment to redo the data sources as needed.
If the above steps didn't help, please open a support case here: admin.powerplatform.microsoft.com/support
Thank you!
The Microsoft Dynamics 365 Customer Insights team
