It would actually help if you could post screenshots from each of the points explained in the long text of the error message, just saying everything is okay does usually not convince us as our experience with freshers here in the space rather confirms that it is not really known where exactly to check.
If you are really certain that none of the mentioned points is addressing the problem then you may need to approach a friendly ABAPer who can debug the program to find the statement which is triggering this message.
But SAP has also a report to delete parked invoices which cannot be deleted: Z_MRM_DELETE_PP see Oss note 501905