Few weeks ago, developers may to deal with the impossibility of sending their iOS apps in the AppStore.
After they upload IPA to AppStore they receiving error about that uploaded application is not unversal (not 64 bit). Currently we know that using Application Loader 3.1 and newer, OSX El Capitan 10.121 and manually installed latest LIPO tools we have successfully published IPA.
My suggestion is simple. Start from installing latest xcode (or update your old one). Lipo and Application Loader come with xcode.
And don’t forget that latest AIR SDK is 188.8.131.52