Opportunity for a Contact Not Displayed in Outlook Integration Side Panel

To resolve this issue, ensure all contacts related to an Opportunity have a Contact Role assigned. Use one of the following two solutions:
Solution 1: Set a Default Contact Role for all Opportunities

1. Navigate to the Opportunity Contact Roles Picklist Values section:
   1. Non-Enhanced Setup Menu: Your Name > Setup > Customize > Opportunities > Contact Roles
   2. Enhanced Setup Menu: Setup > Customize > Opportunities > Contact Roles
   3. Lightning Experience: Gear icon > Quick Find > Search for "Contact Roles on Opportunity"
2. Select the Contact Role you want to set as the default and click Edit.
3. Check the box for "Make this value the default for the master picklist".
4. Click Save.

Solution 2: Assign a Contact Role to contacts on an individual Opportunity

1. Open the Opportunity in Salesforce.
2. Click the Contact Roles related list.
3. If no contacts appear in the Contact Roles section, click New. On the "Contact Roles for [Opportunity Name]" page, use the Search button to select a contact, then choose a Contact Role from the Role dropdown and click Save.
4. If contacts already exist, click Edit next to each contact and assign a Role.

After assigning Contact Roles, select the email again in Microsoft Outlook. The Opportunity and related details now appear in the Outlook Integration side panel for that contact.