E05 means that there is not enough water in the boiler. This has nothing to do with how full the watertank is. Often this error occurs because the boiler lid is not placed properly and therefore the watertank does not close properly on the lid.
If you remove the watertank and boiler cover from the unit, you will see a cross in the center of the boiler cover surrounded by a circle. Inside the circle is a rubber. This rubber, if you tilt the boiler cover at an angle, has a recess through which the water flows. Check if this is right in front of the water inlet of the lid and if so, you can reinstall the boiler lid. This should close very tightly so that it really can’t go any further. The boiler lid should also not come off easily. Next, insert the watertank, it should be at least filled with 300 ml of water. Try to rebuild this 2 or 3 times. If the error code persists, please contact our customer service.