Validate failed after archive: invalid Signature. Code object is not signed at all

Up till yesterday I was able to archive, validate and submit my app project. I'm not sure what went wrong but now after Archiving the project, when I run Validate I get a message "Invalid Signature. Code object is not signed at all".

1. I checked my build settings: in code signing, code signing identify, the release is set to "iPhone Distribution: xxxxxxx inc (ARV8ZG344B) and the prvisioning profile, release, is set to "iOSTeam provisioning Profile: com.xxxxxx.xxxxapp".
2. In the main schema, the Archive build configuration is set to release.

Any idea what should I do to fix it?