This article explains the license SRM license key impact during an upgrade from SRM 8.X to 9.X
VMware Site Recovery Manager 8.X
VMware Site Recovery Manager [VLSR] 9.X
Site Recovery Manager preserves the license only during an upgrade within the same version, for example: from version Site Recovery Manager 8.8.0 to Site Recovery Manager 8.8.0.3.
During an upgrade to a different version, for example: Site Recovery Manager 8.8.0.3 to Site Recovery Manager 9.0 Site Recovery Manager reverts to an evaluation license. After the upgrade to Site Recovery Manager 9.0, you must reinstall your Site Recovery Manager 8.x license key.
When upgrading SRM from version 8.x to 9.x, there is no need to upgrade the license key. The existing Site Recovery Manager 8.x license key will work with SRM 9.X version and does not require an upgrade, but it needs to be reinstalled after the upgrade to version 9.