If error code E2 appears in your display there is a problem with the water supply. It may be that the water pressure is very low or no water is flowing in. Check that the water supply is switched on or that the hose has not got twisted or kinked during the installation which will prevent water flowing into the machine
Tap shown in the 'off' setting
Check it is turned 'on' as shown
It is also worth making sure that the blue tap is not broken. If the valve inside the pipe has seized then turning the blue tap with force may cause it to break, and not actually be opening the valve in the pipe when you are turning it. You may need to call a plumber to repair the tap if it is seized or broken. If you are unsure that water is coming out of the hose a good way to check is by turning the tap off, disconnect the hose and place in a bucket and then turn the water back on. Water should flow into your bucket. If it does not the again a plumber will need to be called out.