I have a Jura Impressa J5 (two actually as I like to keep a spare) which intermittently exhibit the same symptoms - it goes through a brew cycle but no water comes out the spouts but goes into the spill tray instead and the coffee grounds in waste bin feel dry to slightly moist only.
A quick test is to press the centre button of the machine’s control knob so RINSE appears, then press the button again to do a rinse cycle. If water comes out to the coffee spouts then the Brewgroup is connecting successfully and water is passing through normally, except that( in this particular case) there are no compressed coffee grounds restricting the flow of water.
During coffee brewing, the water has to pass through the compressed block of ground coffee as well as the stainless steel mesh filter at the bottom of the plunger and this builds up with more pressure from the pump to push its way through, however, the water comes in through the Drain Valve assembly at the bottom to the Brewgroup, and this valve has two conical rubber seals to hold in the pressurized hot water in, and direct it up through the Brewgroup, and if these seals are weak or there is too much additional pressure in the Brewgroup due to a partial blockage, or coffee grounds that are too fine, them the water bypasses the seals in the Drainvalve and enters the lower water tray.
If you are watching a Youtube video on dismantling the Brewgroup for cleaning, then check the seals in Drain Valve assembly and replace them if necessary.
Remember that if your Rinse cycle has water coming out of the drip spouts, as it should, then your Brewgroup is connecting properly at low pressure, you have to address the issue of the with the high pressure of brewing leaking passed the drain valve.
I hope this help to clarify things.
Regards,
Chris Stevens