I am having the same issue. I am doing mine and my wife's together. I am a full time employee working from home due to COVID, she is 100% self employed.. I obviously claimed the employment expenses, but I did not check anything for her. Hers keeps giving this error message and it kicks me back to T4's to fix, but she doesn't have a T4.
I ended up spending 80 minutes on a service call over this issue. They did try to fix it, but in the end they told me it was not possible to override this error. I was told to start over from scratch, print and mail my return. Utterly abysmal experience. I will not be using TurboTax next year.