Account admins and program admins
In Message, click Import Contacts, then select the appropriate program at left. Click Import Contacts, and upload your CSV file. Uncheck the box to Import new contacts, and check the box to Update existing contacts. A box will appear displaying the field headers in your file. Be sure to select active, but if you included additional columns in your CSV file to update, you can select additional fields.
Choose an error setting (the default option only runs the file if no errors are encountered; the first option runs the file regardless of errors, but gives detailed information on what rows were skipped and why). Finally, click Start Import. Once the file runs, a summary will appear with the number of updated contacts and the number of errors.
We've created a CSV file with two columns: customer_id and active. We've entered the customer_id of each contact we'd like to opt back in, and set every active value to true. We'll save the file as a CSV.
After navigating to Import Contacts and selecting our CSV file, we'll uncheck the Import new contacts box, and check the Update existing contacts box. When the list of profile fields appears, we'll choose to update the active field. We've selected to Only import the file if there are no errors. We'll click Start Import to upload the file and restart the contacts.