Online marketplaces for buying and selling used Gucci handbags, Prada dresses and other secondhand designer goods are finally coming into their own. One of them, The RealReal, had a hit initial public offering last month and is now valued at more than $2 billion. Another, Poshmark, is reportedly preparing for an IPO of its own as early as this fall.  

But the outlook for another such marketplace, Tradesy, appears less rosy. While its competitors saw consistent year-over-year sales growth during each month of last year, Tradesy saw declines during several of those months, according to credit card transaction data compiled by the firm Second Measure. It did, however, eke out about 4% annual growth in U.S. gross sales for the full year, Second Measure said. 

In 2017, Tradesy—which has raised about $100 million in equity and debt from Kleiner Perkins and other firms and was valued at around $155 million in 2016 during its last major funding round—attempted to merge with the Paris-based secondhand fashion site Vestiaire Collective, but the talks fizzled, two people familiar with the matter said.