Greetings.
We are in a hybrid environment working without issues for years now.
Approximately at the beginning of February we got noticed from at least two users that their Office 365 Group was not showing new messages. In the group folder, the blue message counter shows the number as expected but when you click the folder name the message pane shows older messages only. The number of users increased to 6 (at least that we know of).
The synchronization status area shows the message "This folder has not yet been updated.".
Things we have tried:
1. Change the autodiscover dns record on premise to a CNAME record and point it to autodiscover.outlook.com.
2. Opened a support ticket within Outlook and followed all the support instructions (it's been at least 2 weeks since) given by the support representative, all the suggestions given by the support representative within Outlook didn't fixed the issue. They ended up closing the case and suggesting we reached support through our tenant admin portal.
3. Disabling and enabling "Cache Mode".
3a. Something interesting about disabling and enabling "Cache Mode". When we do this step, Outlook will pull messages and update the Group folder to the last message received in the group's mailbox. But when it reaches the latest message received the message "This folder has yet been updated." shows in the status bar and the group stops showing new messages.
This is a weird scenario for us because it's not happening to all users, just a group of users with different properties.
Not all users belong to the same group.
Not all users have the same M 365 apps versions.
Some users that are not having the issue have the same M 365 apps version as some who have the issue.
We created a new group to see if something in those previous M 365 groups might be corrupted and the new group is showing the same symptoms.
Any suggestions are greatly appreciated.
Thanks for your time.
