If your in-app purchase is disabled, you will see the message "was not able to load a product" and the get started button is disabled.
To enable in-app purchases make sure you haven't restricted it previously
- Open Settings on your phone
- Go to General
- Go to Restrictions
and make sure in-app purchase is switch to on. Apple has a FAQ here on this subject: https://support.apple.com/en-ca/HT204396
Also here is screenshot to show you where the in-app purchase switch is located.