If you are setting download limits on your templates, there's bound to be a time when a customer hits the limit for a perfectly legitimate reason. In this case, you can reset the download count for that particular template.
Note: Be sure that your download limit is not set too low or you will incur additional customer service requests in your shop.
How to Reset the Download Count for a Template
Search for the customer in Admin > Orders and type their name, email, or username in the search field. After searching for the customer, click the username of the customer to view the User Details page. Then, click the "Templates" tab and click the "reset" button for the template. The customer will now be able to download their template.
If the customer is currently logged into their Templett account, have them refresh their screen and download again.