No water in parts of house?

Hi there,
So last night we turned on an isolation valve so we could sort out the bathroom taps upstairs. When we came to turn it on again there is now no water to the whole bathroom upstairs 2nd floor, no water at all to the bathroom on the ground floor but cold water to the ground floor bedroom and 1st floor kitchen. So no hot water at all. We have a combi boiler so no airlock.
Any ideas about how to fix it?