The things that come to mind are:
Check your outliner for making sure you don’t have an object hidden in the viewport that is coming into consideration at render time or that your lights render icons are turned off.
Make sure you don’t have compositing nodes enabled. Sometimes you forgot you turned compositing on and you don’t have a render node or maybe some compositing going on with some black color.
Check to see if you have any keyframes somewhere, maybe in the camera.
In any case, you can upload your file and we can take a look and help diagnose the problem.
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