All good advice above regarding the grinder. I had one and it was incapable of producing an espresso grind, even after modifying. I’m now using a Eureka Mignon and couldn’t be happier with it.
One other thing to check is the pressure coming from the machine. As I recall, the Classic leaves the factory pumping around 13bar which enables it to be used with the coffee pods, but normal ground espresso is best made with 9-10bar. If you google it you’ll see how to reduce the pressure and various methods of measuring the pressure, but just make sure the machine is unplugged before you open it up and start tinkering.