3333529 - Approver unable to approve or reject due to Error:' Action not enabled'

Approver is unable to reject or approve the purchase order.

SAP Business ByDesign

After the Purchase order was sent for approval, changes were made, such as the respective project being closed.

Ask approver to send for revision and then click on check button on order, you will see errors if any

For example: error is displayed "Status of project task XXX (not 'Started' or 'Released')

So first release the project  task and take action on this Purchase order, then close the project again.

2206101 - Purchase Order Withdrawal From Approval is Disabled or Greyed out

2216473 - Error message received "Action not Enabled" while Approving Goods & Service Receipt 

Cannot reject; unable to reject; Cannot approve; unable to approve; , KBA , SRD-SRM-PRO , Purchase Requests and Orders , Problem