Why do I still owe Michigan State tax after withholding 4.25%? I don’t have any other income, credits, exceptions, etc.

[xmasbaby0]

MI does have a flat tax rate.   Have you double checked the amounts you entered from boxes 16 and 17 of your W-2?   Look for misplaced decimals or extra zeroes.    

[Mike9241]

we can't see your return  

your tax should be the net of your Michigan wages  box 16 of W-2  less your exemptions from box 9 on the MI-1040 times 4.25%

Maybe your employer miscalculated withholding or maybe on the MI W-4 you claimed too many exemptions  or maybe you mad an enry error.