Water pressure no hot water

Hey there bit of a weird one we have a condenser boiler that has stopped producing hot water but still heats the radiators, we have good cold water pressure upstairs but it’s really bad downstairs in the kitchen but the outside tap on the same main line and 4ft away has good pressure and the boiler feeds off the same line as the both of them the heating engineer said the boiler is working perfectly but the issue is the water pressure isn’t high enough to trigger the boiler to produce hot water and thinks there maybe a leak but couldn’t find one. I’m on the same line as four other houses all with bad water pressure so am considering getting my supply split off but I don’t understand how I can have low pressure and good pressure at the same time.