Worcester 24i junior boiler won’t repressurise ?

Hope someone can help. My old Worcester 24i junior combo boiler stopped heating the water (red error light flashing slowly). Noticed pressure had dropped below 1 bar so turned little tap by the loop/hose to let some more water in. Have done this before and this usually takes only a couple of minutes. Today this hasn’t worked. No movement on pressure dial and can’t hear the usual rushing of water into the boiler. Checked water supply into house and into the loop/hose and that’s fine. Any suggestions gratefully received.