NO explanation for why it was stuck. We did have a rookie fill the tank at one point and may have overfilled which pegged the needle where it was not visible. I know the tank itself is not supposed to permit over fill, but that that's the hypothesis.
When the needle on the tank was not visible the monitor panel displayed one led, or E.
Now that the dial is unstuck it reads just under 1/2 and the panel displays 3 leds, or 2/3 full. There is no reading for 1/2 so I guess it reads on the high side.
Curious that it shows the exact same reading as yours did!
2011 Solera 235S