Tap says open on model jura e75 - Jura Capresso Impressa E75 Espresso & Coffee Maker

SOURCE: jura capresso

The dial on the upper right is all you need to do. Turn from the coffee cup to the water symbol. Water will pour out the spigot from the frother wand so put a cup under it. Close the tap when prompted by turning the dial back to the cup symbol

SOURCE: Jura Impressa E fails to dispense, then gives "open tap" message

I had the same problem, when I called their very helpful customer service, I was given these directions.
Take out the tray.
Inside the machine you can now see a flap hanging from the top.
Reach behind the flap, and you should feel a round object/filter. It has a little dimple sticking out in the middle.
Wipe the filter with a paper towel.
Put the machine back together, and voila you got your coffee brewing again.

SOURCE: open tap - filling system - close tap

Try using warm water in the watertank, important that the water is not too hot, it can cause leakage in the o-rings in the fluidsytem.
Repeat the procedure a few times, if nothing helps, turn off the machine and wait 1 hour and try again.

If you can`t get around this message, then the flowmeter needs to be changed.