Just to be clear, you tried that specific Zoom to Fit All keystroke? Depending on how far off screen the artboard is simply zooming out might not work... although this is odd so I'm not sure the Ctrl and 0 (zero) will work.
Adobe Certified Expert & Instructor at Noble Desktop | Web Developer, Designer, InDesign Scriptor
Just to be clear, you tried that specific Zoom to Fit All keystroke? Depending on how far off screen the artboard is simply zooming out might not work... although this is odd so I'm not sure the Ctrl and 0 (zero) will work.
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Adobe Certified Expert & Instructor at Noble Desktop | Web Developer, Designer, InDesign Scriptor