The Bolt founder claimed a group of investors had signed off on the company’s chaotic $450 million raise, but some said they hadn’t. Now, BlackRock and other investors have moved to stall the round.

Investors know to expect surprises from Bolt founder Ryan Breslow by now. Once it was the staggering $11 billion valuation of his “one-click” payments startup Bolt — a deal that minted him as one of ...