CloudKit error using watchOS 3

Question

I believe I have everything set up right, and everything works for CloudKit in the iOS Simulator, but I can't get CloudKit to work in the Watch Simulator: "Couldn't send a valid signature"

Does anyone know why this would be?

• I know CloudKit works in watchOS 3 per Apple "iCloud interactions. Starting with watchOS 3, the WatchKit extension can communicate directly with CloudKit and other iCloud technologies."

• I already did Settings > iCloud and then log in using your Apple ID
  on the iOS simulator per enter link description here

• In the Watch Extension, I'm calling CloudKit using CKContainer(identifier:"iCloud.com.xx.xx") per enter link description here

• I double-checked Apple's doc to make sure I didn't miss something:
  enter link description here

• I'm accessing the same CloudKit container on the Watch that I am on
  iOS, so nothing is wrong with accessibility to the data in CloudKit

• The CloudKit capability with the container identifier is set correctly in the Watch Target

Answer 1

According to Apple:

CloudKit usage is blocked on watchOS Simulators. Running any test will throw a “Not Authenticated” error even though you are signed in via the paired iOS Simulator. Workaround: Use CloudKit on paired devices with watchOS 3 and iOS 10.

This is from the watchOS 3 release notes, but does not seem to be fixed yet. Just test on a real watch and everything will work fine.