It is my understanding that a batch job will exectue to move the purchase req to the release approved purchase req list page.
I would start by validating batch job setup.
(1) AOS is a batch server...
go to System administration> Setup > Server configuration (Is batch Server is selected)
The appropriate AOS instance name should be selected as a batch server
(2) Batch group blank has a selected batch server
go to System administration> Setup > Batch Group
Click on the blank batch group then select the batch server tab.
There needs to be a server name selected on the batch server tab.
(3) Delete an reconfigure batch jobs (especially if you restored the DB where another AOS was being used)
If the above steps do not resolve the issue, then delete and re-add the batch jobs
(a) Navigate to COMPANY/System administration/Area page > Inquiries > Batch Jobs > Batch Jobs
(b) Select batch job with status executing, click functions and change the status to canceling
(c) Refresh, AX 2012 will change canceling jobs to waiting
(d) Select batch job with status waiting, click functions and change the status to withhold
(e) Select batch job with status of withhold or ended, click functions delete
Re-Configure Batch Jobs
COMPANY/System administration/Area page > Setup > Workflow > Workflow infrastructure configuration
Step through wizard to configure batch jobs
If this doesn't resolve the issue, two more suggestions
(1) Open the purchase req, Click the perform budget checking button (Financials tab)
(2) Check workflow history to ensure there was no stopped error thrown
