If you have a owned license you may run into this error when you upgrade, this is because your support and updates have expired. Why?
If you have 3.3.0 and Blesta releases 3.3.1+ but your support & updates expire, you can still apply the patch however you can't upgrade to 3.4.x if your support & updates have expired.
You can purchase a extra year by clicking Manage > Addons > Support and updates.
Please go to: Settings > System > General > License Key and re-save the license key.