OAuth2.0 works from Postman UI, doesn't work via manual request

Token request works from Postman UI, doesn’t work via manual request

The issue I’m facing is I’m trying to manually get the token from the API for the sake of automation. What I did is I configured IdentitySever to grant token on user credentials it worked fine when request has been sent via OAuth UI:

I’m getting the following request/response (viewed in console):

Now the issue is that I’m sending the exact same request but manually, but it fails:

Am I missing something? The requests are identical, I copied over clients, passwords etc in case anything is different.
I’ve also tried to do the token request via get+query string, but same result

Anything else that I’m missing? Does UI do something else under the hood? Did I miss something?

What do you mean by manually?