@juliaong , I'll reiterate even though you say that you did not enter the amount elsewhere. Amounts reported in box 12 of your W-2 are to be entered only in box 12 of TurboTax's W-2 form, nowhere else in TurboTax. Remove the Roth IRA contribution entry that you made under Deductions & Credits. Nothing reported in box 12 of your W-2 is a Roth IRA contribution. A 401(k) is not an IRA. This applies if TurboTax is reporting an excess IRA contribution.
Note, however, if you made an excess Roth 401(k) contribution (more than the elective-deferral limit) that's a different problem and an actual excess contribution that would need to be corrected.
