Postmates, the on-demand food delivery app that's valued at $2.4 billion, was said to file to go public in September.

It's the last day of the month, and there's no S-1 filing.

Postmates, which is not believed to be profitable, may be exercising caution during a nightmarish year for money-losing consumer technology companies. On Monday, WeWork shelved its IPO until next year.

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Postmates may have to push back the estimated time of delivery on its initial public offering.

The unicorn food delivery service confidentially filed the paperwork for an IPO with the Securities and Exchange Comission in February, positioning it to go public before the end of the year.

And as recently as August, sources told TechCrunch's Megan Rose Dickey and Kate Clark that Postmates would publicly reveal its IPO prospectus, or S-1 filing, in September.

It is September 30, and the startup has yet to deliver.

The year has not been kind to money-losing consumer technology companies, with investors shaving tens of billions of dollars in market value off Uber and Lyft since the two went public. WeWork on Monday canceled its initial public offering after six weeks of intense scrutiny and the resignation of embattled cofounder and chief executive Adam Neumann.

And Postmates has some blemishes that could spook public market investors. Despite a rich, $2.4 billion private market valuation, the company is reportedly unprofitable and lags a crowded field of rivals in the food delivery market.

Read more: How WeWork spiraled from a $47 billion valuation to talk of bankruptcy in just 6 weeks

Dan Ives, an analyst at Wedbush who covers consumer tech companies, said the fiasco at WeWork "has been a yellow flag" for startups headed to the public markets. Poshmark, an online clothing marketplace, and Endeavor, an entertainment conglomerate, also shelved their initial public offerings this month, citing less than ideal market conditions. The situation may cause investors to exercise more caution around businesses lacking profitability.

"The right business models and fundamentals will continue to have an appetite among investors, while more frothy ones will have an uphill battle," Ives said in an email.

A spokesman for Postmates declined to comment on the company's timeline, though people familiar with the matter told Bloomberg's Crystal Tse and Michael Hytha last week that the public offering may be delayed to 2020.

A long-time startup advisor, who asked not to be named because their firm represents many technology companies, said investment bankers and independent board members are "very aware" of the market conditions and will be discussing with their companies what needs to be done to protect their investments.

"Everyone will want to avoid the need to make any adjustments in public, but rather to make them in advance and in private so that the IPO process goes as smoothly and successfully as possible," they said in an email.

Founded in 2011, Postmates' most recent funding round of $225 million gave the startup a valuation of $2.4 billion earlier in September. The new capital could signal the company is running out of cash, though it's also not uncommon for companies to try to boost their valuation ahead of an initial public offering.

According to data research firm Second Measure, Postmates is the fourth-largest food delivery service by consumer spending, behind its better-funded competitors DoorDash, GrubHub, and Uber Eats, which is part of Uber. Still, Postmates sales were 69% higher in August 2019 than they were in the same month a year prior.