Welcome to the Community, @npalmieri.
Thanks for letting us know this has worked in your QuickBooks before. I'm here to get you pointed in the right direction for the missing client's collaborator messaging tool.
This was currently reported as an ongoing issue in QuickBooks Online, and our product engineers are diligently working to find a resolution.
We’re continuing to work on solving for this unexpected behavior and we would want to let you know once we come up for a fix. To receive resolution updates via email, I recommend contacting our QuickBooks Online Care Team to be added to the list of affected users.
You can find their contact information at the following link: https://community.intuit.com/articles/1145770.
We value your patience while dealing with this concern. I'll get back to you here in the Community space once this issue is resolved.
This information should get you in the right direction. Feel free to post your comment below if you have other questions aside from this. I'm always here to help. Have a great holiday week.