If you were subscribed to the 14-day free trial or to a subscription plan (Starter, Advanced, Pro), and the plan has expired, your API key will become invalid.
When your system or mobile app sends an API Request with an invalid key, a QR Code image with a preview watermark will be returned.
See sample below:
Such QR Codes are unscannable by most QR Code scanning apps.
To activate your API key, login to your account and start/extend your subscription.
If you still have questions, feel free to reach out to our support team at firstname.lastname@example.org