Hi,
Some users report that, after we migrated from Exchange 2010 to Exchange 2016 on-prem, they cannot add a Skype meeting in a shared mailbox calendar. The following error pops up;
The user accounts in Outlook and Skype for Business do not match. Please make sure you are signed in to both applications with the same user name and privileges.
I renewed the Outlook profile for one user, but that did not solve the problem.