Apologies everyone, there is an issue with the FREE version where it incorrectly tells you that you need a subscription to update to the latest version. This is NOT the case, free users will NEVER need to buy Stackable to get plugin updates!
To update, follow these steps:
1. Navigate to Plugins > Add New
2. Search for “Stackable”
3. Click on “Update Now”
Alternatively, you can deactivate Stackable plugin, then update it. Or you can manually update Stackable by downloading the v3.1.5 plugin zip file and uploading it into your site.
The issue happened because a flag was accidentally set that made the update notice think that the free version was premium when it comes to updates.
Thank you everyone for reporting this issue. This issue shouldn’t be present in the latest version.