Why might a company have a negative P/E ratio?
Cfefinances
A company has a negative P/E ratio when its earnings are negative — that is, when it is operating at a loss. Because the denominator of the ratio is negative, the P/E itself becomes meaningless as a valuation measure.
Think about what happens to the ratio when earnings go negative. With a loss in the denominator, the P/E turns negative and stops being meaningful.