POST requests will use application/x-www-form-urlencoded by default. You need to add Content-Type: application/json header, be it manually or some software/tools do it automatically.

Before trying on your target site, we recommend using a testing site like httpbin.io to see if the parameters are sent correctly.

Check that the parameters are sent and that the format is correct. In case of doubt, switch between both modes to see that the changes are applied correctly.

For more info on POST requests → How do I send POST requests?

Can I get the cookies from the responses?How do I send POST requests?