The Lattice software will validate the node-locked license by checking the NIC address of the PC where the software is running. If the NIC address does not match the address in the node-locked license file, the software launch will fail.
Your new PC has a difference NIC address from that in the license file. Therefore you will get the license checkout error.
You willl need to request a new license for the new PC. Please refer to the licensing page at http://www.latticesemi.com/en/Support/Licensing