I just purchased a used Gaggia Espresso Color (not sure how long it's been used nor maintenance) and am running into an issue (doesn't happen every time) where when I turn on the pump to pull a shot you can hear the pump on and working but no espresso comes out.
After 20-30 seconds the sound from the pump becomes quieter. But, if I turn the pump off for a few seconds and then turn it back on espresso does start coming out.
This is my first time making espresso so not sure if it's user error or an issue with my used machine. I just ordered some descaler online to descale it as I'm assuming the machine hasn't had much maintenance.
For reference I'm using a medium roast and a Baratza Virtuoso grinder.