No hot water after refilling tank

Hi guys,
Spent my morning reading manuals, forums and websites but cannot figure this out! Just moved into a new flat with a pulsacoil 3 and discovered the water in the refill tank was too low and therefore there has been no hot water. I've filled the tank up to the required mark and now have two green lights on the front panel but still no hot water, this was about an hour ago.
I have checked the LED on the circuit board which has two flashes then a break, as far as I can can see this means the system is functioning normally.
All mains switches are on and I have the timer board set to 24 hours just to be sure it's on - there was an orange light on the board before but this is now off.

I should add that when we looked around the flat a few weeks ago the boiler was very warm and clearly functioning correctly. The upper tank level must have fallen below the minimum in this time and shut the boiler off, of only I could work out how to get it back on!

The boiler is buzzing but still no hot water, any ideas?

Thanks,

Max

Update:

Its all working. I turned everything off at the mains, left it for a while and then back on. The light in the timer came back on and luke warm water started from the tap. A few hours later and I have hot water, just time in time for evening showers.