The most common problem with espresso machines is that they get clogged
up with minerals from hard water. Just run some vinegar through it. Put
the vinegar in the reservoir, run some through, stop it and let it sit
for a while and then run the rest through. Then run some more water
through and make sure all the vinegar is out. It won't affect the coffee
much but it will affect the milk. Once the vinegar has been purged it
will be as good as new.