Are the correct size grounds being used?
Check to see if coffee grounds are too fine or tamped too hard. If using a pod to try in place of fresh coffee and it works, there is no problem with the espresso maker.
Does the machine need to be cleaned?
If you have recently descaled, the showerhead may have debris present, which will prevent the water from passing through the filter basket. Remove the showerhead and clean it thoroughly.
Is the hose attached properly?
Check to see if the clear tube has been pulled down to the bottom and the reservoir is full. Press and hold espresso button for 30 seconds and water should flow through. If not, remove Portafilter and repeat this step.