First, are you able to see Write Latency metrics for these LUN's in other places in the product? What device type is it?
Second, do you see any data if you change the selector from "All" LUN's? I can't tell if the product is trying to graph multiple LUN's at the 0 line since the legend is cutoff.
Third, does data appear if you change the time selector at all? It's possible we don't have roll-up data (or only 1 data point) yet for the device at the 24 level if you just started collecting data.