FIrst you need to check the nodes are actually connected to each other and in sync. For example look at the blocks field of getinfo on both nodes.
Second after importing the private key into the 2nd node, you need to make sure you didn't pass a false value for the rescan parameter, which would prevent the node identifying old transactions using the address for that private key. If you did do this, you can stop MultiChain, then re-run it with the -rescan parameter.