teekoh, if you can twist your body enough to get your eye up to the enlarger lens, you'll be able to look inside and likely see what the problem is.
It'll be bright, so you might want to use an extra-dense negative, or neutral density filtration, or even sunglasses. If it's too bright for you, don't persist. (If your eye can't focus, rack the enlarger lens in a bit, as though making a very large print.)
I've never used one of those enlargers, but my guess is that a light baffle or similar is not fully seated. Good luck.