I would point you to our docs about essentials and the way it functions as a primer around the cause of this situation… Specifically this section:
The Portworx Essentials license requires that your clusters be connected to the internet and send usage data to PX-Central. Portworx Essentials clusters connect with PX-Central once per hour to renew license leases. Lease periods last for 24 hours, ensuring that any temporary interruptions to your connectivity do not impact your cluster
There’s also an FAQ in this section of the forum you may wish to have a read over about, which explains more.
As for your specific case - we would need to understand if you’re a.) using this on a set of hosts that have no outbound internet connectivity (so called “air-gapped” in our docs) - in that case, you will need to provide access to a proxy that can be used to satisfy the end-point connectivity requirements for essentials. Please search the forum for other people’s experience with this approach as needed.
Additionally, only one Essentials cluster instance is allowed per PX-Central user, so setting up a 2nd essentials cluster for example will invalidate the first (as that’s another source of issues).