Hi@Deshmukh, Vijit thanks for the question.
To clarify you are using KUDU to update webconfig file? is this a production workload? Did you deployed your files through run from package? if yes, this means your folder is set as Read Only.
0 means write mode and 1 is read-only mode
You can try to redeploy your app or change the setting WEBSITE_RUN_FROM_PACKAGE value from 1 to 0 via the Azure portal in the configuration Blade.
when you change the value to 0 you should go back to KUDU and doublecheck D:\home\site\wwwroot
please see this blog post for more infomation: https://dotnetthoughts.net/azure-app-service-kudu-409-conflict/
NOTE: keep in mind that following this process will reset your webapp to initial state - all your deployed code, assets and all will be removed.
Please let us know if you have more questions.
Best,
Grace