Profile & for project planning board does not exist

What causes this issue?

If the WBS element has activities, you must delete the activities first.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Delete activities, or with "Adjust dates" adjust the WBS dates to match
the activity dates.

Error message extract from SAP system. Copyright SAP SE.