Unlock xcode files?

In my case (react native) was a problem with node_modules. I just remove it and made yarn install. Probably, they were installed with sudo so xcode hasn't permissions.

If anyone is here using Ionic Cordova with the same issue, Michael's answer works but you must go to the parent directory which is the ios folder and the Apply to enclosed items will show up there.

Remember the Project isn't just a standalone ".xcodeproj" file but it's actually a folder that contains a number of hidden items.

So when applying permissions, make certain to apply permissions to every item in your project folder.

You can do this via the "Apply Permissions to Enclosed Items" popdown menu (available in the "Get Info" window), which looks like this: