What causes this issue?

You are trying to start a program in test mode, but according to the
status management information the data selection for this program has
already been completed in update mode.
If you run the program in test mode, the data in the conversion cluster
may be deleted, which in turn would lead to inconsistencies in some
conversion scenarios (delete-insert logic).

System Response

For this reason, it is no longer possible to start the program in test
mode.

Error message extract from SAP system. Copyright SAP SE.