I think I know what is going on
your content type is set to empty
try to change to this:
make sure it's all in one line and nothing left below
When I set my Postman like yours, I get nothing on my logic app:
-------------------------------
Here is my complete POSTMAN setup:
Make sure is "POST" , select body to add the json and select 'raw' and 'json""
minimun headers:
No Auth
Try again with those settings.
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