Hi @HarshD ,
I used a similar method on my side to configure Flow, which can update PromotedState.
The only difference with you is to change the double quotes to single quotes in Body, as below:
Please take a try again.
I also tested it with double quotes, and it can also update the value of PromotedState.
We can demote or unpromote news using following list view extension
Join us for a FULL day of FREE Microsoft Flow Sessions from some of the best minds in the industry!
Continue your learning in our online communities.
Features releasing from October 2019 through March 2020
Fill out a quick form to claim your user group badge now!
Check out the new Microsoft Flow Community Blog Topic Suggestion board!
Learn how to build the business apps that you need
Find out where you can attend!
Watch & learn from the Flow Community Video Gallery!