My control number on my W2 is not working

[LeeM]

You can simply leave it blank. The IRS doesn't care what's in Box D because its use by payroll departments is optional. 

A Control Number (Box D) is used by many payroll departments to uniquely identify a W-2 in their system. 

Now, if you're trying to import your W-2 and you're persistently being asked to enter something in Box D, click skip import to get past this screen and manually enter your W-2 (which should only take a few minutes anyway).