This error message suggests that the Purchase Order in Dimensions no longer matches the Purchase Request in FocalPoint.
In order to post an order from FocalPoint to Dimensions, all lines in Dimensions must exist in FocalPoint still and have the same quantities, values etc - if they do not, then this error occurs.
The best way to resolve this error is to:
Log into Dimensions
Browse to Purchasing, Orders
Select the relevant order in the list and click Delete (piece of paper with a red cross) icon
You should now be able to approve and post the Purchase Request in FocalPoint as before without the error appearing. This will also recreate the Purchase Order in Dimensions.
If any line on the order has been fully received or invoiced however, you will not be able to delete it and will therefore need to manually update the lines so that they match, either in FocalPoint or Dimensions.
Please note that only lines in FocalPoint with a tick in the "Linked" column need to exist in Dimensions. Any new lines that have been added in FocalPoint will be automatically added on to the order in Dimensions when it is approved and posted through.