Hi ihm185
Delivery Proofs generally run into this error because the 'operationMgt' workflow has already picked up your Delivery once.
Previously it was suggested that this could be controlled by decreasing the value of 'nmsOperation_LimitConcurrency' option, thereby reducing the frequency of 'operationMgt' Workflow. However that's not really ideal since this issue was identified as a known Bug with some previous Build and clients were then recommended to move to higher Builds in which the fix was rolled out.
Another remote possibility could be that the Delivery is in 'Ready to be Delivered' state thus no more proofs are being sent out.
If that's the case, you could manually update the Status of the Delivery by doing a 'mass update of selected items' for your Delivery and changing the Status to 'Being edited'.
Then try sending the Proof again.
However our recommendation would still be a Build Upgrade if your Instance is on a lower Build.
Which Build is the Instance on?
