I cant think of any reason why the yeast wont eat the sugar. I have done 30+ batches and never had a problem like this (it is my first Berliner Weisse though)
I brewed a Berliner Weisse with a starting gravity of 1.040 but it wont ferment at all.
4 lbs German Pilsener
4 lbs German Wheat
.5oz Hops
Mashed the 8lbs of grain at 150 for 60mins. Cooled the wort to 120 degrees and added .5 lb acidic malt. Covered the wort in saran wrap and let sit...
I used to get some condensation in mine until I added some moisture absorbing powder. I replace it every couple if months. I think it is called Damprid