First make sure you have the Stackable Premium installed and not the free version of Stackable, and that you have your license key activated.
If your account under Stackable > Account in your WordPress dashboard incorrectly shows your account as Free, you can try the following to fix the issue:
In Stackable > Account, click on the Sync button on the upper right of your account details area. Refresh the page afterwards and see whether this fixes the problem.
In Stackable > Account, click on the Delete Account button on the upper right of your account details area. Doing this will only delete your account details stored in your site, and will not actually delete your Stackable Premium account.
After doing this, you will be asked for your license key again. Enter it to activate your copy of Stackable Premium, this should fix the status of your website.
If the first two steps above do not work or if you can't perform them. In Stackable > Account, click on the Start Debug button.
Afterwards, you should start seeing your license information. From here, you can either click on Delete Account (perform step 2 above), or click on Activate Plan.
This should update your license information. After this, click on the Stop Debug button.