Post request to NetworkInfrastructures not working

Issue in API Playground
I'm attempting to add a dedicated IP address for a customer using the following, but when I click on submit, nothing happens:

But I'm expecting to see something similar to this when I submit:

The console shows this error:

However, I don't think that this is invalid syntax as I've used this exact syntax before. I'm not sure what is wrong with it... it's not very fancy.
Subsequently, if I click on the "Get Request" button for networkInfrastructures, nothing happens. Nothing is logged to the console or network in the debugger.

Comienza reproduciendo la solicitud POST en API Playground e inspecciona los errores de consola y de red mostrados en el issue. Comprueba por qué el POST de networkInfrastructures y el GET posterior no producen ninguna respuesta visible; se considera terminado cuando ambas solicitudes se envían correctamente y devuelven los resultados esperados.

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