Friend's trial version of Dorico Pro running slow

He was complaining about a lag in sound when entering notes (he claims about 2 seconds). He also said that Sibelius runs super smooth without any issues. Any idea what might be the trouble here? I know this is hard to diagnose without knowing any of the hardware specs or seeing if he is running simultaneous software but are there any typical culprits for this sort of thing on the trial version of Dorico 5? Thank you!

Usual culprits are audio drivers on Windows (though D5.1 should improve things); large numbers of third-party VSTs; also “MIDI feedback loops”.

But, yes: without knowing any specifics, it’s almost impossible to tell.

High latency in audio could be caused by having the wrong ASIO device chosen in Edit > Device Setup, or having a too-large buffer size chosen.