You gotta keep in mind false negatives are most commonly caused by user error and the test not detecting enough COVID antigens in the sample. Antigen tests gauge infectiousness. But even if you have symptoms you may still test negative because your body isn’t producing enough of the measurable antigens. So the antigen tests are one good tool to help gauge when you are no longer infectious.

If you’re testing negative after 14 days but still have symptoms then you might still be infectious.