Outlook Integration Error: "MISSING LABEL__ PropertyFile - val" When Logging Events (Lightning Sync All Events Setting)

To verify and resolve this issue, follow the steps below. A Salesforce administrator must review the Lightning Sync configuration assigned to the affected user.

Verify How Events Sync to Salesforce (Salesforce Administrator Steps)

1. Navigate to the Lightning Sync Configurations page:
   1. In Salesforce Classic: go to Setup | Outlook Integration and Sync | Settings
   2. In Lightning Experience: go to Setup | Email | Outlook Integration and Sync
2. Click on Let users sync contacts, events, or both between Microsoft Exchange and Salesforce under Lightning Sync.
3. Navigate to Define Sync Settings in the Set Sync Settings and Check Status section.
4. Click the Go To Configs button.
5. Click on the name of the configuration that the affected user is assigned to.
6. Check the Sync Settings section. Look at the Which Exchange Events Sync to Salesforce column and confirm whether the value is set to All Events.

If the value is All Events, this confirms the error is caused by the sync configuration. The user cannot manually log events while this setting is active.

Resolution: Change Sync Method to Allow Manual Event Logging

To allow the user to manually log events, a Salesforce administrator must change the event sync method from All Events to Events Users Select in the Lightning Sync configuration.
When the sync method is set to Events Users Select, users control which individual events are synced to Salesforce and can also manually log events through the Outlook Integration side panel.

Workaround: Use Automatic Event Relating Instead of Manual Logging

If changing the sync method is not possible, an alternative workaround is to enable the Automatically relate Exchange events to Salesforce records option in the Events Data Set. When this option is enabled, Exchange events that sync via the All Events method are automatically associated with related Salesforce records. This means users do not need to manually log events because the association happens automatically.

Known Limitations When Using the All Events Sync Setting

When a user is assigned to a Lightning Sync configuration with the All Events sync method:

• The user cannot manually log events to Salesforce records from the Outlook Integration side panel.
• The user cannot log events to unrelated Salesforce records.
• The user cannot edit and save changes when selecting the "Edit Logged Event" option on events that already synced via the All Events setting.