When the touchpad lights flash on a Lisa it means the fill cycle has 'timed out' - in other words, that when the machine has tried to fill the boiler up to the correct level, it has taken too long. This either means the boiler was a long way below the correct level (or even empty), or that there is a flow restriction slowing the water flow into the boiler. If you turn the machine off and back on again it 'resets' the warning and has another go at filling the boiler - watch the sight glass through the hole in the front panel on the right hand side and you should be able to see the water level visibly rise when you turn it on and it tries to fill. If you can see the level rising, just turn it off and back on again when the lights start flashing - it sometimes takes half a dozen cycles like this to get the boiler level up to its operating level from empty. If you don't see the level rising, then there is probably a blockage in an inline filter somewhere. If the flow through the heads is Ok then any blockage is likely to be in the filter at the entry to the fill solenoid, which hides under the drip tray under a small stainless steel cover panel.
Be careful - if the boiler is empty (check via the sight glass) then turning the machine on can damage the element by heating it in air rather than submerged. If the power switch has positions 0, 1 and 2, then just switch it to 1 to fill the boiler before switching it to 2 to heat once the boiler is at the correct level. If there is only 0 and 1 on the switch, turning the machine on will power up the element, so the water level has to be above the minimum level before you turn the machine on. The black plastic knob sticking partway out of the right hand end of the panel below the drip tray (assuming it's a Lisa and not a Lisa R) is the manual fill lever, pushing that in will manually add water to the boiler (assuming the machine has mains water pressure feeding it).