United were at Harrogate for the latest of their Youth Alliance Cup group fixtures on Tuesday afternoon.
Harrogate took a one-goal lead into the break but that was doubled on the hour.
Nic Bollado pulled one back for the Blues, but two late strikes from the hosts put the result beyond doubt.
"We weren't at it today and we were punished," youth boss Mark Birch said. "It was disappointing but there are lessons learned and things for us to work on."