The code released June 29 contained a defect where multiple proofs were being generated. A fix was applied the morning of June 30 which required users to log out and log back in for the fix to take effect. If you do not log out and log back in, the fix is not applied.
A side effect of this bug:
Proofs created 1) before the fix was applied AND/OR 2) pre-User log out / log in may report ERROR GENERATING PROOF when dropping a 2nd Version on top of the bad proof.
The solution is to delete the bad Version of the proof (the one that was created during the time the bug was in the system) which will expose the previous Proof version. This will allow you to drill down into the previous Proof without the Error so you can refer to any comments or changes.
Steps to cause Bug:
1) You have a proof that was created during the Bug period.
2) You drop a 2nd document Version on top of above proof document.
3) You receive "Error Generating Proof"
1) Highlight the document in Workfront (under the documents tab)
2) Click Details (either on the document name or in the right hand column)
3) Scroll down to the Versions area.
4) Click the top level Version.
5) You will be prompted with three options.
6) Choose Delete > Are you Sure > Yes, Delete it
7) This allows you to Access the previous Proof version.
This is only if you need to refer to the previous Proof version for any comments, changes etc.
Unfortunately, this proof can no longer be updated with another version.
If you need to use it for other versions you will need to create a new document and proof it, then move forward using this new proof. The new proof will accept new versions etc.
The old proof can either be deleted or kept for reference.