Lost sound

Hello I was listening to my playback for editing when I can only assume I must’ve bumped something and now my sound is not working. Can someone help me get it back? I have read through all the lost sound articles I found and have checked volume control, mute, recording device etc. thank you.

What sort of sound card is it?
Is it an internal sound card or USB or something else?

I expect by now everything is working OK. If not, have you tried rebooting?