what does it mean when there’s a 0 in a company’s total revenue and operating revenue?

i hope this question is allowed here. i'm looking at the income statement for a few companies that mine lithium, and 4/6 of them say they have 0 total revenue, and they've had 0 since 2019-2020. does anyone know what this means? it's messing with a calculation this how-to video mentioned when trying to pick which companies to invest in.