LambdaExecutionError from CloudFront

Serverless Framework
1

I am trying to deploy Lambda@Edge using following yaml

serverless.yml 
> service: viewer-request
> provider:
>   name: aws
>   runtime: nodejs12.x
>   region: ${opt:region, 'us-east-1'}
>   stage: ${opt:stage, 'staging'}
>   memorySize: 128
>   timeout: 10
> 
> functions:
>   viewerRequest:
>     handler: handler.viewerRequest
> 
> resources:
>  Resources:
>   IamRoleLambdaExecution:
>     Type: "AWS::IAM::Role"
>     Properties:
>       AssumeRolePolicyDocument:
>         Statement:
>           - Effect: Allow
>             Principal:
>               Service:
>                 - lambda.amazonaws.com
>                 - edgelambda.amazonaws.com
> plugins:
>   - serverless-offline

Then set trigger

Event type: viewer-request
Include body: No
Path pattern: /images/*

But when I try to access web contents I get following error

2020-08-17	20:47:53	EWR52-C4	1274	72.79.124.96	GET	r1gcva4mhojctg.cloudfront.net	/images/email_icon.svg	503	https://stage.domain.com/	Mozilla/5.0%20(Macintosh;%20Intel%20Mac%20OS%20X%2010_15_5)%20AppleWebKit/537.36%20(KHTML,%20like%20Gecko)%20Chrome/84.0.4147.125%20Safari/537.36	-	-	LambdaExecutionError	nkMyhXkEzWo6CMsOdS7qNS-fszUuQJ-FW6UDxYdKqxOuSoQmffKVwA==	stage.domain.com	https	48	1.472	-	TLSv1.2	ECDHE-RSA-AES128-GCM-SHA256	LambdaExecutionError	HTTP/2.0	-	-	52571	1.472	LambdaExecutionError	text/html	1019	-	-

Anyone know what I am missing here ?