400 bad request rails error for an end point that exist

Question

I have a route DELETE /api/v2/users/:user_id/devices(.:format) api/v2/users#delete_device {:format=>"json"}

and can be seen when I run "rake routes"

The problem is that when I try to hit this end point in postman , it gives me 400 bad request

localhost:4000/api/v2/users/123/devices

It is not only giving me 400 bad request for this route but for half of the old routes too.

The response I get from postman with 400 status code is :-

{ "errors": [ { "code": "unknown_platform", "description": "Unknown platform" } ] }