Help understanding an error message from Dukt OAuth plugin I'm using the Dukt Twitter plugin which requires the Dukt OAuth  plugin.

Both are working perfectly on both my local Dev environment and the remote Staging environment, but not on the Live site. Both plugins install with no errors or problems. Configuring the OAuth plugin (for Twitter only) is fine as well - it accepts the keys/credentials generated from the Twitter API Management Console and shows as "configured" on it's status screen.

However, when I then go to the actual Twitter plugin config and hit the "Connect to Twitter" button, I get this error message:

Fatal error: Class 'League\OAuth1\Client\Server\Twitter' not found in /webserver/domains/[CLIENT]/live/craft/plugins/oauth/providers/Twitter.php on line 46


Anyone have any idea what this error message means?

I suspect it's more to do with the server or site config than the actual plugin but I'm not sure where to start looking as I don't understand why it can't find that namespace
It was indeed missing files, as suggested by Alec and Benjamin. All down to some non-specific .gitignore rules that meant it was ignoring all "src" folders - which is one of the folders created by the composer install

Thanks for your help guys!