Ionic ios issue with firebase

Hi developers around the world,
i stuck in a serious issue while using firebase for push notifications in ios. Its working fine in
android. I made corressponding certificates APN key, downloaded the “GoogleService-Info.plist”
file and moved it to the location but getting the error again and again. i am using “phonegap-plugin-push” plugin. Below is the error:

Failed to fetch APNS token Error Domain=com.firebase.iid Code=1001 “(null)”
2018-08-23 11:59:25.468825+0530