The body of the request is not valid json

We are using Azure translate to translate our app to several languages. We get a response when we do a GET request for all the possible languages, However, when we do a post request we get this error message " the body of the request is not valid JSON". Has anyone come across this error? Here are some screenshots

Here is documentation: Translator Translate Method - Azure Cognitive Services | Microsoft Learn

Here is documentation for Authentication: Translator V3.0 Reference - Azure Cognitive Services | Microsoft Learn

Any help would be appreciated. Thank you all

@Harri_Sarsa, @Mevi, @Cecilia, Do you guys have any recommendations? Thank you for your help

We were able to resolve it with a formula. Thank you!