The control number (box D) is not required to enter your W-2 or complete your tax return. Simply leave this number field blank or skip this question of TurboTax, click Continue and you will be directed to manually enter your W-2.
It appears that some employers or payroll processors specified that the control number is required to import your W-2. However, they left the control number off of the W-2. In this case you will be required to manually enter in your W-2. This is an error made by your employer or the payroll processor.
Please see the following FAQ article for additional information. https://ttlc.intuit.com/replies/4417180