Lighting problem or bug?

Hi everyone, I’ve been using blender for about a year now - so I’m not a complete newbie. I have a problem that suddenly developed in a .blend. Up until about 20 mins ago my world background, set to sky texture, used to show up in render or render preview, now it doesn’t.

I have checked that Film Transparent is off, the background is visible to the camera and all the usual settings. What’s weird is that the room I am lighting has some lights (spot lights), some emission planes outside and the sky background - but the background and outside emission planes are not rendering - they are just black.

The emission planes are having no effect on the room but the background seems to - if I turn Film Transparent on the background turns transparent, turn it off and it turns black. If I make the background bright pink instead of sky then the room is infused with pink but the outside of the room remains unaffected and looking through the windows to what used to be the sky is still black???

I can’t find anyone else who has had this problem, is it a bug in the file (if I start a new blend then everything works fine - I even reset all the settings to default and the problem still persists) or is it possible that I have accidently turned something on or off?

I have had strange problems with this particular .blend before, basically if I can avoid having to scrap the whole thing and start over then I would like to.

Any help would be greatly appreciated!


Did you accidently switch off perspective?