Plug Power's the name and hydrogen fuel cells are its game. (Unfortunately, investors would prefer Plug play for profits). Image source: Getty Images.

What happened

It's Monday and stocks are soaring, with the S&P 500 Index (SNPINDEX: ^GSPC) up 1.9% as of 11 a.m. EST. But not all investors are sharing in the joy. In particular, owners of Plug Power (NASDAQ:PLUG) stock are suffering through a sell-off that sent the shares down as much as 15% before it recovered to a 12.7% loss.

So what

Earnings (or rather losses) are part of the reason for the sell-off. This morning, Plug Power reported a $0.07-per-share loss, significantly worse than the $0.05 loss that analysts had told investors to expect and a penny-a-share worse than the company's $0.06-per-share loss in Q3 2015.

Even more frightening than the loss, though, was the evaporation of Plug's revenue stream. One year ago, Plug Power reported total revenue of $31.4 million. Last quarter, that number shrunk by almost half, falling to $17.6 million as sales of the company' "fuel cell systems and related infrastructure" plunged 77%.

Now what

Those numbers seem to fly in the face of management's assertion that "Plug Power continues to show growth and improvements in all areas of the business during the third quarter." To the contrary, you have to look long and hard to find anything growing, or improving, at all. When you do find it, it appears in the company's income statement, where Plug revealed that it earned gross margins of 2.2% on its sales in Q3 2016, an 11-fold improvement over the 0.2% margins posted in Q3 2015.

Sadly, with revenue plunging and administrative costs climbing (up 10% to $13.6 million), the improvement in gross margins didn't come close to producing a profit for Plug today. And with investors selling off the stock, it appears they've little confidence tomorrow will be any different.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.