We were having the same issue. Our users are on Chrome, we found that when they switched to Incognito mode, it would work but that's not a permanent fix. When I called Support, these are the exact steps they gave us to resolve it and so far it's working.
Clear Cache & Cookies for all time in the b...
Our project managers generate the proof, send it to appropriate stakeholders and notify Traffic when all revisions/comments are final. Traffic then adjusts the schedule as needed and the designer accesses the proof to implement the revisions. We have such a high volume of projects and daily deadline...