Customer Manager may not appeard on Outlook ribbon when there are multiple accounts linked to the outlook profile. You may create a seperate outlook profile and use only the Office 365 Business Premium account on the profile.
The following are steps to create a new outlook profile:
1. Open control panel (right click the windows icon and select “control panel”)
2. Search and open "mail"
3. Select “Show Profile”
4. Make sure to select “prompt for a profile to be used” and click “Add”
5. Name the new profile (e.g. OCM)
6. On the pop-up screen, click “Connect to a different account.
Enter your Office 365 account credentials and complete the set up. Once the mail profile is set up. Close and reopen outlook. Select the new profile when prompted