It does sound like an airlock, I managed to sort my machine, with the same problem, by doing the following:
Phase 1: fill water tank and with machine turned OFF and everything set to dispense cold repeatedly put the water tank on and off. This pushed water into the system, you can check it is working by looking for air Bubblé rising in the water tank as you do it.
After approx 40 cycles (probably equivalent to 1 mug of water) or if water starts “leaking" out the back of the machine clean up any residue/spilled water.
Phase 2: *please ensure all spilled water is cleaned up so the unit and area is dry!
Refil water tank, put into correct position and turn machine on, with capsule holder and lever in dispense position. Waitt until green light shows then switch lever to hot water position. CAREFULLY lift and replace water tank “pushing more water” until it dispenses water by itself.
Use the rest of the water in the tank to flush through. I cycled between hot and cold.
Phase 3: celebrate!