First, are both employer plans HDHP (High Deductible Health Plan)? If not, then you are not permitted to contribute to an HSA and all contributions would be excess. Do you have any other insurance?
Second, is the $1,640 the value of the amount with code W in box 12 on your W-2?
Third, when you saw the screen "Let's enter [name]' HSA contributions", did you see the code W amount on the first line and make no entry on the second line?
Please come back with your answers, as it is possible to have TurboTax think that you have an excess contribution when perhaps you didn't...
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