Contacts are not synchronized with Einstein Activity Capture

Question

Hello,

I test Einstein Activity Capture to synchonize contacts and emails between Salesforce and Outlook in a sandboxe.

I followed the trailhead (https://trailhead.salesforce.com/en/content/learn/modules/outlook_integration/outlook_integration_unit_3) and I use the user-level oauth method to connect Salesforce to Outlook.

I created a configuration for Einstein to synchronize all contacts, I added myself as User.

In "My settings", I connected my account with Office 365.

I have 3 contacts in the sandboxe and 2 others contacts (with different email address) in Outlook.

Unfortunately after few days, no contacts are synchronized in Salesforce

Do you have any idea why there is no synchronized contact in Salesforce and in Outlook?

Thanks