TikTok is breaking download records and taking over pop culture. But experts say it faces challenges in turning user growth into profit.

· With 315 million downloads in the first three months of 2020, TikTok set a new record for the most installs by any app in a single quarter, according to the app analytics firm Sensor Tower.
· The short-form video app has entered mainstream culture in a big way in recent weeks, attracting new users outside of its core Gen-Z...