https://www.cnet.com/news/apple-restores-facebooks-ability-to-run-internal-apps/

Apple blocked Facebook from offering the Facebook Research app to iPhone users. Facebook sidestepped Apple's review process for consumer apps by going through a program that allows companies to create apps for their employees to use and test.

The iPhone maker then revoked Facebook's enterprise certificates, which affected apps that employees used internally including a workplace version of Facebook and an app to hail rides.