If you paused your QR Code in order to activate our Free Plan, you likely can't unpause it because it's not a Dynamic Website URL QR Code.
The only Dynamic QR Code type available with the free plan is the Website URL QR Code.
If you’re unsure of your QR Code type, you can look at the label above the QR Code name, as indicated below. In descending order, the QR Code types are PDF, Social Media, and Website.

Alternatively, you can look at the icon to the left of the QR Code name. The Dynamic Website URL QR Code icon is shown below.

You can always upgrade your account to reactivate and create more Dynamic QR Codes.