No summary created - it says 'summary unavailable' in individual email summaries in einstein email summaries

@Gobinath A

Einstein Activity Capture is for reps to connect their emails and calendar account to Salesforce -so that emails and events are automatically added to the activity timelines of related Salesforce records. 

We think the reason for not able to show the email summary -may be due to email content being too short. 

Thanks for your help.