I encountered this error while developing my first WatchKit app. Followed guidance from @PureRushh, @Antonioni and others to dump the contents of:
~/Library/Logs/CoreSimulator/CoreSimulator.log
The log contents led me to the error. I'll include the details in case others encounter this error while developing WatchKit apps.
Log message:
com.apple.dt.Xcode[89555] : installApplication:withOptions:error:: Error Domain=IXUserPresentableErrorDomain Code=1 "This app could not be installed at this time." UserInfo={NSLocalizedDescription=This app could not be installed at this time.,NSUnderlyingError=0x7f9ab87d1f20 {Error Domain=MIInstallerErrorDomain Code=101 "WatchKit 2.0 app's bundle ID com.somecompany.AirTime2.watchkitapp is not prefixed by the parent app's bundle ID followed by a '.'; expected prefix com.somecompany.AirTime."
Cause: I had modified the value associated with the BundleIdentifier key in the Info.plist (via General-> Bundle Identifier) of the parent app to match a URL Type (for SSO redirect); however, I failed to update the WatchKit App Info.plist value associated with the WKCompanionAppBundleIdentifier key (see second bold line).
Fix: Modify the WatchKit App Info.plist value for the key WKCompanionAppBundleIdentifier to agree with parent app's bundle ID