HOW CAN I FIX THE PRESSURE ON MY WORCESTER BOSCH GAS BOILER?

The reset button is flashing red every second and the blue light every 2 seconds?

We think it could be lack of pressure as the pressure gage is not moving and there doesnt appear to be any other problem!

We have a manuel stating dt20 programmer for greenstar i and greenstar si models but it does not give any help on this problem?

We are not even sure of the actual models name?

No heating or hot water, very bad indeed, please help!