As @SweetieJean stated - Leave the Control Number out - it is not part of your tax return, will not keep you from e-filing and won't create an error with the IRS. If it was imported, delete it.
Many Form W-2s have a "Control Number" just above where the Employers Federal ID number (EIN) is located. The "Control Number" is for the employer's/payroll preparer's internal use. It is not part of your tax return.
See I have no box D or Control Number on my W-2 for additional information and guidance, if necessary.