When you setup a migration with Import2, you will be asked to connect your HubSpot account. It is recommended to connect your HubSpot account using a Super Admin user profile, in order to reduce the chance of errors arising from lack of adequate permissions.
Please login to the HubSpot user you will be using for the migration, and follow the steps outlined below:
From the sample migration setup page, select "Grant Access" to HubSpot.
Select the HubSpot account you wish to migrate data to.
Confirm the access you are granting, by selecting "Connect App".
Now you are connected, and can click "Start Sample Import" to begin the free sample migration.
If at any time you need to remove the Import2 app from your HubSpot account, you can follow the steps outlined here.