Hi josephhyt,
How many users in your organization have the same issue?
What do you do before this issue happened?
If this issue is on certain users, clear the client cache and check if it works. Here are the steps:
- Right click the Windows icon and open the Run bar.
- Then type in: %localappdata%\Microsoft\Office\16.0\Lync\
- Delete the sip profile folder.
- Go into the Tracing folder, delete all files, but not the folders.
If no luck after clearing the cache, please try the repair an Office application as the following article shows:
https://support.office.com/en-us/article/Repair-an-Office-application-7821d4b6-7c1d-4205-aa0e-a6b40c5bb88b.
Moreover, check if the message is displayed on missed conversation. Also check the conversation history in outlook client.
If all users in your organization are affected, please check if there is any related error message in Lync server event viewer. And check if there
is any conflict on firewall.
Best Regards,
Sharon Zhao
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