“Your license quota of production site(s) has been reached”
If you are getting a notice that your license quota has been reached, you can try the following to fix the issue:
1. Check sites that are still active with Stackable Premium
If you are transferring your license key from one domain to another, be sure to deactivate the license key first before trying to re-activate it in another.
You can check your sites in your Stackable Account page https://wpstackable.com/account/ in the “Websites” section.
2. Check that the Premium license is not active on the site with another registered email
Sometimes the site you are trying to activate is already activated with Stackable Premium, but the site is registered with another email.
3. Deactivate the Premium license from your Stackable account
You can deactivate your Premium license from your Stackable Account page: https://wpstackable.com/account/
Currently, deactivating a website doesn't automatically deactivate the license. However, the license can be deactivated through the details panel of the selected website in the “Websites” section by clicking on the "Deactivate" license button.
The license can also be deactivated via the "Licenses" section (instead of the "Websites" section) by clicking on the "Deactivate" button.
This way though, the license will be deactivated on all sites, but this wouldn't be a problem if a license is a single-site license.
Related docs:
Still Stackable Free even after Activating My License
I have upgraded my account but when I try to Sync the License, the plan remains FREE