It sounds to me like a bad connection, or, if there are any, a cold solder joint. Use your meter and test the volt across the string of cobs. Then check the amperage, by placing the meter in series at the beginning of the circuit, between the driver and the first cob. Disconnect the cobs from the driver test the wire connection to each cob for resistance, it should be zero. LEDs flow electricity in only one direction, be sure you connect your leads positive to positive, negative to negative. You my find at least one with some resistance in it. If so its a bad connection.
It could be a bad driver but I doubt it, meanwell has a very low failure rate.