A friend updated Cocoapods in our project. When I pulled the latest stuff from git I got the following error:
Pods was rejected as an implicit dependency for
Also make sure that your podfile targets the same iOS version your project targets:
For example, if you're targeting iOS 10.0 in your Xcode project your podfile should include platform :ios, '10.0' at the top, too.
Per this solution, which was the problem in my case.