Hello,
As parnassus pointed out, your issue is due to the license being invalidated. This happens because the SN of iMC is tied to the MAC address of the primary/active NIC of the iMC server. If that changes for any reason - it could be cloning or a dynamic MAC configuration on the NIC or otherwise - then the SN of iMC will be re-generated and the current license will thus become invalid.
To resolve this, you would need to transfer your license from the current system to the new one. You can do this on the My Networking site, where you can initiate a license transfer yourself a few times. If you run out of transfers or prefer not to do it yourself, you would need to open a support case with the licensing team to assist you. You will need to provide them with the current and new SN of your iMC systems to perform the transfer.