It is no longer possible to use X (formerly Twitter) and Bitly for authentication with OAuth.

For X: [phpBB Debug] PHP Warning: in file [ROOT]/includes/functions.php on line 2462: Undefined array key "Failed to request resource. HTTP Code: HTTP/1.1 401 Unauthorized"

For Bitly: An error occurred while processing your OAuth request.
As a reminder, the following links have been added to the applications:

https://www.domain.com/ucp.php?mode=login&login=external&oauth_service=
https://www.domain.com/ucp.php?i=ucp_auth_link&mode=auth_link&link=1&oauth_service=

In the end, either Bitly or Twitter is used.