The watsonplatform.net endpoint URL is retired. Update your code to use the specific watson.cloud.ibm.com URL for your service.
I am getting the above error in my facebook chat bot.
I have created new API service credentials as per this link
https://cloud.ibm.com/docs/watson?topic=watson-endpoint-change
and added it to ibm cloud.
https://website.region.mybluemix.net/
getting 404 for this.
Where should the newly created api endpoint be updated for facebook chat bot to work ?
Did you look at the Watson Assistant integrations topic that is linked to from the end of that endpoint change topic?
https://cloud.ibm.com/docs/assistant?topic=assistant-release-notes#6April2021
There is some information about facebook,
with more details.