Popular messaging app company Line's strong stock market debut is quickly becoming a distant memory.

Line (LN) pulled off the biggest tech IPO of last year, raising $1.3 billion from selling shares that soared when they started trading on markets in New York and in Tokyo.

Fast forward to the start of 2017 and things aren't looking so pretty.

Line shares plunged 11% in New York on Wednesday and 10% in Tokyo on Thursday to their lowest levels since the IPO.

The reason? An earnings report that fell short of expectations and revealed that the app is losing users.

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Line shed 3 million monthly active users globally during the fourth quarter of last year, dropping from 220 million to 217 million.

Line's management touted "big opportunities" for the app during the IPO, including expanding to other geographic regions. But the latest numbers don't bear that out.

The company's user numbers are stronger in the countries where its app was already popular: Japan, Thailand, Indonesia and Taiwan.

It did report profits of 7.56 billion yen ($66.5 million) for 2016, compared with a net loss of 7.58 billion yen the previous year. But analysts and investors' were scrutinizing Line's user and sales growth, and expected more from the messaging empire.

"Our impression is negative," JPMorgan analyst Haruka Mori wrote in a note to investors.

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Line's messaging platform offers a range of "content services" like mobile payments, on-demand taxis, and music and video streaming.

While Line is the fourth highest grossing app in Japan, according to analytics firm App Annie, revenue from content services was lower last year than in 2015. The company also reported slower growth from games and digital stickers.

Line's moneymaker last year was ads, accounting for nearly 40% of revenue. The company said it expects advertising to deliver "steady growth" in the coming months.

But analysts remain wary.

"We expect investors will need confirmation of strong growth in performance ads before turning bullish," Mori said.