If you haven't previously filed the return that the W-2 needed to be reported on -- for two years ago -- you can still file and receive any refund that you might have coming.
If you filed for that year, then it's not too late to file an amended return. Generally, if you'll receive a credit or refund by filing an amended return, you have to file Form 1040X within
3 years (including extensions) after the date you filed your
original return, or within 2 years after the date you paid the tax,
whichever is later. So, you should be fine filing an amended return.
Please see the TurboTax FAQ "How to amend (change or correct) a return you already filed", below.
https://ttlc.intuit.com/replies/3288565