One of the problems I see quite often is that Microsoft Office Skype for Business will stop syncing calendar items with exchange. This becomes an annoying inconvenience for those trying to join meetings from Skype for Business from the calendar tab.
To resolve the issue, try the following steps:
- Validate that Skype is set to sync calendar items
- Click Tools -> Options -> Personal
- Check the option “Update my presence based on my calendar information,
- Clear the local appdata cache
- Close Skype
- Delete the folder with the email address in the name under: %userprofile%\appdata\local\microsoft\office\16.0\lync
Hope that helps.