If you need to make changes to the marketing allowed flag to many customers, it is easiest done through the web dashboard. You will need to do the following:
1. Go to Customers-> Enroll Customers and hit Export CSV
2. This will download your customer list in a format like the below
3. Next, In column G change all the Marketing Allowed from NO to YES, in the spreadsheet program. Please make sure to fill up all the "Marketing Allowed" column to "Yes" in the csv file for those customers eligible to receive your offers and have given you permission to market to them.
5. Next click on "Import CSV" to begin importing
6. The Customers in your list will be imported and synced with your Clover Customers database as well
The customers will be given another chance to opt in or out through a text message. But please do not change the marketing allowed to yes for customers who have already opted out.