Starting with Consul 1.14, and patch releases 1.13.3 and 1.12.6, Consul will disallow upgrades to new versions with a release date after license expiration: If you are looking to upgrade to a version of Consul that was released after your license expired, please be sure to renew your license before attempting an upgrade.
This feature requires HashiCorp Cloud Platform (HCP) or self-managed Consul Enterprise. Refer to the enterprise feature matrix for additional information.
Consul Enterprise enables the capability of automatically upgrading a cluster of Consul servers to a new version as updated server nodes join the cluster. This automated upgrade will spawn a process which monitors the amount of voting members currently in a cluster. When an equal amount of new server nodes are joined running the desired version, the lower versioned servers will be demoted to non voting members. Demotion of legacy server nodes will not occur until the voting members on the new version match. Once this demotion occurs, the previous versioned servers can be removed from the cluster safely.