I recently had a few problems with signing my apps due to some Xcode 8 changes, mainly the difference between using PROVISIONING_PROFILE_SPECIFIER and PROVISIONING_PROFILE to specify your provisioning profile.

There are wonderful blog posts out there that describe the process in detail, here’s what I found important:

• PROVISIONING_PROFILE_SPECIFIER setting is used to indicate the type of signing method that should be used for a given target. Targets that want to employ the manual method of code signing will not use this setting, and will instead use the deprecated PROVISIONING_PROFILE build setting. If the setting is set then, the new automatic code signing method will take over.
  Source: pewpewthespells

• The name set in PROVISIONING_PROFILE_SPECIFIER has to match your provisioning profiles name. Not the filename, not the UUID, the actual name set under the <key>Name</key> in your provisioning profile. Nothing else, to the best of my knowledge and my tests, there’s not magic matching happening, just a string comparison! Source: Testing//FizzBuzz Project