If you have access to the terminals on each LED, the Fluke in diode mode should illuminate each individual LED (This is not always the case). The polarity of the meter leads is important. If no light when connected one way, try reversing the leads.
If not, count the number of diodes in each strip, multiply it by 3 (3V per LED) gives you the voltage you need to apply to the input of each strip. So a strip of 12 LEDs will need 36V. Any strip that doesn't light up will have faulty LED/LEDs on it. Heat discolouration on a particular LED may give it away.
Most of us have a LED tester by now. Connect it to a strip, and it automatically adjusts the voltage up until the strip lights up.