NEW YORK—It’s one of the downsides of apps that make things like ordering food or buying stocks and cryptocurrencies easier: What happens when something goes wrong? It’s often a frustrating chase, tapping through menu after menu in hopes of reaching a person to fix the problem. It’s also something that upstart companies upending the investment and trading industry are increasingly acknowledging. Robinhood, the app that helps more than 22 million people trade stocks and cryptocurrencies, announced Tuesday that it’s offering 24/7 phone support for its customers to cover almost every issue. It follows up on an announcement by Coinbase, the cryptocurrency trading platform that said last month it would launch 24/7 phone service by the end of the year for many customers. Before its own stock started trading on the public market for the first time, Robinhood cited “concerns about limited customer support” as one of its challenges. Earlier this …