Very Odd Issue With Playback

[Snafu]

Hello peeps,

having a very unusual problem- playback as stopped after working fine for about 5 years!! Recording still works, the waves are all still there, I can even hear the audio I record in while recording..but then I press play, the master levels appear normal (visually) but no audio comes out whatsoever!! Cables and Amp not the problem either, I think it's the first time I'm stuck for options here!!

Any ideas/help would be greatly appreciated...

PS: No mutes are on either, and the mix buknob is turned to the right..Still must be something obvious, everyhting was working til yesterday. It's an old 6.4cs9 on Mbox1:)