In order to change the Status of a specific transaction:
Log in to Dimensions
Click on Purchasing or Selling as required
Click on Orders
Find and highlight the required order
Click Edit (pencil and paper icon)
Click on the Blue Arrow beside "Status is on Hold" at the top of the order
Double-click on the required status to change it
Click Save on the order to save the changes and save it back into the batch
If orders seem to regularly being set to Hold automatically, the Dimensions profile settings may need to be changed.