Cubase pro 12 playback issue

New to 12 but not new to cubase.
System was working fine, just finished recording/mixing and mastering a song for a client.
Next day wont play back. No updates on system since.
Interface is fine (will playback mp3 or wav in media player) scarlett 18i20
Audio is working fine in cubase in the media bay or the import window
Audio is fine if sampling sounds on a vst instrument
Hit play on a project and nothing but poop. No playback audio from mono or stereo channels, no playback from some vst instruments. playback on some vst instruments but early.
Huge what the heck as 12 hours ago it was fine with literally no changes to anything in between.
any help would be appreciated as i have a “walk in” song to record for an mma fighter with a tight deadline and i know he can knock me out LOL