My application facebook now is Golive. I subscribed page "A" and i got message but i try to subscribed page "B" but i don't receive any event from webhook

Now i will check permission user give access to my application i got page "B" like a page "A"

step to repoduce :

1. Use the user token to call the API GET: /me/accounts?fields=picture,access_token,name,cover to list the pages with access tokens.
2. In the response, there will be a page named "B" . Copy the page token.
3. Use the page token to call the API POST: /pageid_B/subscribed_apps?subscribed_fields=name,messages,message_echoes,messaging_postbacks.
4. Try sending a message to the page "B".

Expected result: - Receive an event from Facebook.

Actual result: - Did not receive an event from Facebook.

Please help me . What else should I check? Thank.