&4 You cannot remove marketing project &1 from scenario &2

What causes this issue?

You cannot remove marketing project &V1& from scenario &V2&. This
marketing project is either one of the committed projects, or it cannot
be set to either active or inactive.

System Response

The system has not removed this marketing project from the scenario.

How to fix this error?

If the marketing project is one of the committed projects, do one of the
following:
Cancel the marketing project (by changing the project status)
Remove the project from the planning scope of the scenario set
If the marketing project is not one of the committed projects, see the
error log.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.