Apparently there isn't enough red in that eye for Lightroom to detect the color to correct. On my monitor, I'm able to see more red in the other eye, but I see very little (if any) in the one that you have chosen to fix. But then, maybe I'm colorblind.
I don't know. The crosshair on the left eye is not centered on the area containing the red. That would be my only observation. Having dealt with a lot of redeye.