i'm using sandbox account for development APIs, currently working POSTMAN for API testing.
i'm able to get response (GET request) using sandbox account but my PATCH and POST requests are not working. 

{{base_url}}/Company('CRONUS USA, Inc.')/workflowCustomers 

Headers are:

Content-Type:application/json

If-Match: {{etag}} // W/\"JzQ0O0l5cm16TGF3c253cGlSSG8yY0cwOTRqL1c0cDcxM3NaWlpBRm1iYjJVQlE9MTswMDsn\"
and i'm trying to update city
Request Body:
{
"city": "...."
}

but getting Request Data Invalid error. 

kindly help me to sort out this issue.