I haven't updated since the whole diamond-hunt thing, so it didn't occur to me -
I think you now need to place a selector tag in the electrolyser to get single item
recipes to work with the new double input slot.
Do you have a selector tag set to zero in one of the input slots?
If you do and it still isn't working then it looks like it might be a bug.
wow, i feel incredibly dumb for forgetting that.