Once you have undergone an antibody test and it turns negative, you have not developed antibodies to the SARS-CoV-2 virus. It shows that:
You were affected with COVID-19 in the past and have not yet developed detectable antibodies. We can't really tell for sure that all infected persons are always going to develop antibodies that can be detected.
It may also be possible that you may have been given a wrong negative result. This type of result is usually called a false negative. The test may fail to detect antibodies even though you have them in your immune stream.