Hello,
You can check following settings:
1. Depending on the environment, there may be two Activities (Regarding) entities in the Related drop-down list that refer to different entities in Timeline, ensure you select the right related entity. Also, you can set the Related to Appointment (Regarding) directly.


2. Then I know you want to show the Actual End time in Last Meeting Data field. Select “Mark Complete”, the Actual End field will show the actual end time of the appointment.


3. Now you can try to Recalculate again, the Actual End time will be shown in the Last Meeting Date.
