When there are alpha Hydrogen's why can't it show tautomerism?
You could sort of devise a tautomer by transferring an $\alpha$ hydrogen from carbon to oxygen. But if you draw the resulting structure you find a pair of cumulated double bonds. That tends to be unstable, and since the cumulated double-bonded carbons favor a 180° bond angle putting them into a relatively small ring makes them a lot more unstable. Your proposed tautomer is way out there in energy.
Tautomerization of a ketone works better when you have an $\alpha$ hydrogen on a saturated carbon atom.