Slack integration for a bot deployed in GCP

Hi,

My Rasa bot is deployed on a Google Cloud server and is running at https://botuniverse.app. I am having trouble integrating with Slack. When I try to enable events in Slack, I get the below error:

Error: Your request URL didn’t respond with the correct challenge value. Update your URL to receive a new request and value.

The url I am providing: [Rasa X]

I do not see an error when I provide the same url under the ‘Interactivity’ tab in Slack. Tried a lot of options suggested in related topics but to no avail. Can anyone please help?