In order to send feedback requests to repeat customers, you first need to ensure that the Repeat Customer Feedback setting is enabled. To do this, click Settings > Feedback Settings, and locate the Repeat Customer Feedback toggle.
If the toggle is OFF, then you will not be able to send any feedback request to repeat customers, and they will be filtered out when doing a bulk import.
If the toggle is ON, you will also need to set the number of days before a repeat customer can be sent feedback requests. For example, if you set the number of days to 1, you can send the customer another feedback request after 1 day has passed. If you set it to 14 days, then you can send them another feedback request after 14 days have passed. If you have the toggle on, and are attempting to upload a repeat customer before your set number of days has passed, the customer will be filtered out. If you're uploading a repeat customer after the set number of days has passed, then they will be uploaded, and can be sent a new feedback request.
To see how to complete a bulk customer import, please see our Help Article - Bulk Customer Import.