Hello !
Yes ! I had this problem and went through two people in developer support before they asked me to pull the trigger and go through developer tech support , which is a different department. Here is what they said:
"As with all app extensions, the bundle identifier of a Sticker Pack extension must be a unique reverse DNS string that is prefixed with the containing iOS app's bundle identifier. For example, if your iOS app has the bundle identifier com.example.apple-samplecode.myapp, then the WatchKit app's bundle identifier should be com.example.apple-samplecode.myapp.stickerpack. You are receiving a validation error because your sticker pack's bundle identifier does not satisfy this criteria."
So, first notice that when you are in Xcode looking at the General Pane for your project. Notice the " Targets": the app itself signified by the " A" icon made of pencils, also known as " the parent app". Also notice the extension of this app, as signified by the circled "E" icon, AND ALSO KNOWN AS THE " EMBEDDED BINARY". The app and the extension must have different bundle IDs. Moreover, the extension ID is just the appID with something added onto the end, such as " .stickerpack " or whatever.
bundle ID for app
com.yourcompany.yourappname
bundleID for extension
com.yourcompany.yourappname.stickerpack
My problem was that I had made the bundle IDs for the app and the extension the SAME THING. This is incorrect.
You input the bundle ID in the general pane of the app, and you input the bundle ID of the extension in it's general pane.
Simple. Build, archive, validate and upload ! Yay !