Unfortunately, if you have an excess 401(K) Contribution, you won't be able to E-file your 2018 returns.
There is currently an e-filing issue within TurboTax related to excess contributions so you will need to mail in your return. You can check out this TurboTax FAQ for more information: Excess 401(k) Contribution Preventing E-filing.
If you haven't done so already, follow the steps in this link to include the excess contribution as Wages on your 2018 Tax Return: How
to treat excess 401(k) Contribution.
