Why calling AWS APIGateway from .Net framework 4.6.1 gives internal server error unlike .net 6.0 gives OK status?

Why calling AWS APIGateway from .Net framework 4.6.1 gives internal server error unlike .net 6.0 gives OK status. The same exact code using httpclient & same timeout 30 seconds.

Because I was using httpruntime 4.5.1. I replaced it with 4.6.1 stackoverflow runtime version issue