This particular error indicate that HubSpot was unable to sync some of your data because at least one of the selected contacts in HubSpot has been merged into another contact in Salesforce.
When you are reviewing a HubSpot contact and locate the Salesforce Sync section on the left-hand side, you'll see an error message that your contact was deleted and an option to Resync.
- In your HubSpot account, click your photo or avatar in the top right-hand corner, then click Integrations.
- Click Settings next to Salesforce.
- Scroll down the Deleting Contacts from HubSpot section and check the two Delete the contact in HubSpot when a Salesforce lead/contact is deleted boxes.