Lex V2 responsive card buttons not working in Facebook Messenger

Hi! I created a responsive card with buttons in Lex and made sure all fields were filled out (image, title, subtitle, button title and value). It works fine in the Lex console. However, after clicking the button in Messenger, the chatbot returned nothing to the user.

I already tried subscribing to messaging_postbacks in webhooks (actually I subscribed to every field related to messaging whenever I could, just in case) but it didn't work. Could someone please help me with this issue?

My webhook subscription:

Nothing returned after clicking the button:

The bot worked well after I manually typed in the keyword: