Jenkins Chained Build Job failed Issue

https://engineer.kodekloud.com/public-review?task_id=64688eb5c1ff5e7e05478f29&user_id=64ad9e4c803455eea0a8c02f

I am in stuck with this question, tried it almost more than 10 times!

As you can see it is working fine but when i ran the pipeline my jenkins server show me 503 server error!

dont know what to do, I am solving this question through pipeline type not freestyle, kindly help me in this regard.

Thanking you!