I can only think of two items that could be causing this. Since the water level looked good then the right tube when looking at the machine is blocked or the group head is. There is a little stopper and spring in the group that could be preventing flow due to scale.

The difficult part of this for me is that the machine is like new, so when I went to descale it there was no scale to descale. I have descaled all of the parts going from the grouphead to the boiler, and made sure there wasn't any restrictions. It still has the same issue, I just haven't found another way to look at the issue past what everyone has already suggested. Looking at rancilio's parts manual, it seems this machine has the boiler of the pump version of the Classe 6, not the leva (as shown in the pictures too). I can recheck the pipes leading to the group on the right hand side, and the check valve underneath the group, but everything looked clean when I descaled it.

can you post pictures of the piston? are all the tiny holes clean and clear on it?