10.5 - Cubase mutes all audio

Hi there,

I am a complete newb to Cubase, so am just getting used to how it all works at the moment.
I have watched loads of Youtube videos for beginners, so I would say I know quite a lot e.g. keyboard shortcuts, draw and cut tools etc.
Earlier today, I was working on a ‘tester’ project and everything was working fine.

But I plugged in some headphones into my computer (normal headphone jack inserted at the side of computer) and suddenly the audio stopped working - I couldn’t hear anything.
Taking the headphones out again, there was still no sound when I played back my track. The track isn’t muted.
Then I found that no audio was working on my computer - Spotify, YouTube didn’t hear anything either when earlier the audio was working fine. If I close cubase, I can hear perfectly again on YouTube and Spotify. So, I concluded that I cannot hear anything when cubase is open.

I have restarted my computer about ten times, updated my computer, closed and restarted cubase, installed ASIO4ALL and tried that - nothing worked.

I was hoping someone could help me out? I feel like I have tried everything under the sun and nothing has worked.

The VST Audio System is set at Generic Low Latency ASIO Driver - just as it was when it was working. I have also tried with the ASIO4ALL driver - still nothing.
In Audio connections: My computer’s speakers are set as output (Realtek High Definition 1 & 2 for left and right)

My computer is a Windows Surface Pro 6, with a 64-bit operating system and x64 based processor

I do not have an audio interface, but earlier cubase worked brilliantly, so I presume having one doesn’t change the situation.

I hope I haven’t done anything wrong or stupid or somehting is wrong with my computer! Please help!