When users want to comment, some of them are presented with a request to log in twice, and then still fail afterwards.
Other users are able to log in and immediately leave a comment.
When it fails, a user is first told to log in to comment; pressing login give the usual login screen
User is directed back to the page, where the comment box shows the user logged in.
Entering a comment, user is told that (s)he cannot comment without being logged in.
This does appear not limited to users created with/linked to the oneall Social Login plugin, but the issue only occurs when this plugin is active. the behaviour doesn't change with the (de)activation of other plugins.
Disabling the plugin, having the user log in and comment, and then enabling the plugin again solves the issue for that one user.
Answers
Which version of Wordpress are you using ? (confused by your title :-)
Is your site accessible, if so what is the URL?
Finally, can you enable debug (lo log files only if you prefer) and see if you get any message?
Thanks.