UnityAds does not work with Cocos2d v2 for IOS

My app is an iOS app written developed using Cocos2d v2 a long time ago.
The code is still complied and run on the latest XCode 8.3.
When I try to integrate UnityAds, it failed during the initialization, with the following messages:

[UnityAds initialize:delegate:testMode:] (line:68) :: Initializing Unity Ads 2.1.0 (2100) with game id 1472485 in production mode

UnityAds: -[UADSInitializeStateConfig execute] (line:139) :: Unity Ads init: load configuration from https://config.unityads.unity3d.com/webview/2.1.0/release/config.json

UnityAds: -[UADSInitializeStateLoadCache execute] (line:178) :: Unity Ads init: webapp loaded from local cache

UnityAds: +[UADSWKWebViewApp create:] (line:42) :: Succesfully loaded WKWebKit framework

UnityAds: +[UADSApiSdk WebViewExposed_logError:callback:] (line:49) :: {"message":"model: ClientInfo key: applicationVersion with value: undefined: undefined is not in: string","name":"CheckValueError"}

- unityAdsReady event is not called
- My game UnityAd Id is 1472485
- I tried to implement UnityAds on a simple test iOS app, and it did work, I have no idea why it didn't work in my game.
- You can reproduce the problem by downloading the Cocos2d-ios v2 64 bit from here: http://cocos2d-objc.org/downloads/ and then implement UnityAds there.

Can someone pls help me with the issue. Thanks