I have created a form in HubSpot and create a list to sync to Salesforce. When I submitted the form, the data will store on HubSpot, but the data doesn't store in Salesforce. I have mapped all the form fields.
Do you see any sync error; either on the right panel of the contact record, in the Salesforce section; or in Settings > Integrations > Connected Apps > Salesforce?
If so, this resource could be a could starting point for you:
If you're still experiencing issue with this, I would recommend connecting with HubSpot Technical Support, as Support is included in your subscription and they will be able to provide real-time assistance for this matter.