Hey there,
I just figured this out, so I thought I’d share. On line 42 of liveblog.php, the edit_cap constant is declared; this sets the minimum required permission for posting updates on the liveblog.
The original line 42 looks like this:
const edit_cap = 'publish_posts';
By default, publish_posts is an Editor-level permission, so you need to a replacement permission that contributors have – I chose edit_posts.
So, your replacement line 42 should look like:
const edit_cap = 'edit_posts';
Hope this helps!