Most of the users are facing problem on siri suggestion or siri result when you type anything in spotlight search box. In siri problems you will get overlapping result on home screen or not perfect result after disabled/ after apply restriction still app showing in result, Siri suggestions removed from spotlight search in iOS device. Now for new iOS 9 users, Siri suggestion new compare to old search. Here you can try more than one possible solution on Siri suggestions not working in iOS 9.
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Fix: Siri suggestions not working in iOS 9: iPhone/ iPad
Update your device: With beta releases, Apple fixed most of problem related improvements, Siri search and many more. So you have to make your device up to date with latest iOS version. Check Setting > General > Software Update (Current iOS version is iOS 9.0.1)
Restart your iPhone, iPad
Soft restart works in this case, (Press and Hold Sleep/ Wake button). Or Hard reset your devices (Press and Hold Home button + Sleep/ Wake Button at once for 10 seconds continuously). Until Apple logo will appear on screen. More help: restart iOS device
This works in 85% case, when your Siri suggestions not working in iOS 9 – iPhone, iPad. Still are you not solve your problem then go to next fix.
Disable/ Enable Siri Suggestions
Some internal error, disabled your siri suggestions request as a turning off, so you have to repair it by enable/ Disable manually under the Go to the Setting > General > Spotlight search > Siri suggestion.
Search result will be enable for all apps
You can customize search result appear on spotlight search for particular app from above screen.
Possibilities on siri suggestion not working properly more on older iPhone models (iPhone 5S/ iPhone 6/ iPhone 6 Plus, iPhone 6S)
Best of luck, this will works perfect for Siri suggestions not working in iOS 9 on iPhone/ iPad. Any suggestions and alternate solution on this post share with us.