If Box 2 is blank on Form W-2, it means that no Federal taxes were withheld.
On Form W-4, the employee reports their filing status, allowances for dependents, additional deductions for which they wish to reduce their withholding, and any additional amounts they wish to have withheld from their pay.
Enter the amounts on Form W-2 in the Wages section of TurboTax. If you believe the W-2 amounts are in error, contact the employer. If there is no withholding being deducted from current pay, your spouse can prepare and submit a new W-4 to the employer.
See this article for more information.