Purchase Order is in status "In Approval", when the workflow status is in error.
Reproducing the Issue
In the App Manage Purchase Order select the column Purchase Order Status--> See " In Approval".
Workflow Status Column is Workflow with errors
The Purchase order was locked by an user before the workflow could get automatically approved therefore the status of the Purchase Order is still showing as "In Approval".
If the po is opened before the approval process starts from my inbox app, there is a pop-up message and stop the approve/reject process.
However if PO is edited after approval process starts, the pop up can´t be sent.
In automatic approval case, technical user(SAP_WFRT) tries to lock PO, if any user edits po at the same time then also the pop up is not posible.
If the workflow is failed for any reason then such workflows will be listed in the app "Workflows in status error" with the Administrator Role.
In this app you can find the reason why the workflow for the PO for which approval has not gone through completely, you can select the entry and choose "Resume after error " , this way it will re-run the process and the PO will be approved( if the PO is not getting updated by any other process at the same time).
Do not choose restart the workflow option.
KBA , MM-FIO-PUR-PO-WFL , Purchase Order Workflow , Problem