If you know the model number of the faucet, all of the current parts lists are on the www.groheamerica.com website. SOme of the faucets have strainers on the inputs, so the cold could be plugged up. It's possible that some crud is caught in the cartridge or in the attached hose. It is also possible that the shutoff at the wall has a problem (was the flow good when you disconnected the hose? I think you said yes, then it is not likley the shutoff.).