Artificial intelligence startup Sentient Technologies seemed to have hit paydirt three years ago when it landed customers such as shoe retailer Zappos and shoe maker  Skechers for its software, which uses AI algorithms to recommend products to shoppers. But in the past year Sentient has stumbled in efforts to diversify into advertising and agriculture. And lately the company, whose founders helped develop the technology used in Apple’s Siri, has seen an exodus of top executives and employees.

Uncertainty about Sentient’s future was fueled by executives telling customers and employees that it was raising a new round of capital late last year—and then not announcing anything. In its ups and downs, Sentient, which has raised $175 million since its founding in 2007, appears to symbolize challenges facing older AI startups in an increasingly crowded market.