I was confused by this error too. Here's what I found. This seemed to be caused by an old and apparently now invalid QA activity link.Example: Adding ?at_preview_token=[your token here...]Solution:1. Add ?at_preview_token= with no token value2. Clear cookies as this value is persistedThe above steps resolved the issue for me. If this keeps happening to people in your org, they are probably using an old preview link that was provided a while ago and is now invalid for some reason. At least, that'...