Python flask request.form not working in IIS

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Python

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I have deployed a Python in IIS, Application working fine in my local machine.

I am able to retrieve project_id value from below request.form in local machine code but in IIS its not working.
request.form['projectdetails[project_id]'] I am passing values through Json.
When code execute above code in IIS I'm facing exception:- 400 Bad Request: The browser (or proxy) sent a request that this server could not understand. Again, same code is working in my local machine.
I have implemented token based authentication.

What I have tried:

I tried to log str(request.__dir__()) & str(request.__dict__) and compare with my local machine log but its similar and it doesn't display form values in logs for both.

request_form_dict = request.form
for key in request_form_dict:
            logging_config.LogException("create project key logs",str(request_form_dict[key]))

above line also throws exception 
400 Bad Request: The browser (or proxy) sent a request that this server could not understand.