That's funny, because TurboTax owns Credit Karma. There's nothing to fix here.
If TurboTax detects your FICA withheld is lower than it should be (it's a very clear formula, very simple math) you'll get the W2c notice. It generally means your employer made an election that you are probably not even aware of. It's not a program error, but it's also not really anything you need to be worried about. That is all they mean by "ignore the message" - that it isn't anything that really matters, it doesn't mean it is a "glitch".
