I am EXTREMELY new to Glitch and have very very minimal coding/development skills, so I’m aware that this could be a frustrating question. I’m dinking around with remixing a FB messenger bot, and am already stuck setting up the webhook callback URL.
Hmm… it could be a few things. Just to check - did you set the VERIFY_TOKEN value in your Glitch project’s .env file with the same value you used for the Verify Token in the screenshot above? What do you see in the logs in Glitch when you’re trying to verify the page?