Ionic 3 issue while building the IOS Build

I am working on ionic 3 app and i am using one Signal plugin for showing notification. And i have set that if platform is IOS then i show them a page from where user reject to receive notification and accept it.

And when i make the IOS build it will be stuck on the page where user have to select to receive notification or not and in Xcode it shows the error that

Could not signal service in ios 11.4.1
And when i search for solution i found something that we have to install two more plugins which are these.

cordova plugin add cordova-plugin-wkwebview-engine
cordova plugin add

and this plugin cordova plugin add cordova-plugin-wkwebview-engine needs the cordova-ios version 5.1.1

i updated to that but till now am unable to resolve it.

i won’t found any solution from last two to three days.