The solution or explanation depends on how you are sharing your paper URL: via an auto-post or via the social sharing column (see below) on your paper.
Situation (when sharing your paper URL, applies to both auto-tweets and sharing manually)
Sometimes mentions are not included
Promo-tweet only features 1 or 2 contributors ( or maybe none..) when there is room for more...
When promoting the paper URL, we have a logic in place that only allows one name to be mentioned within a 48 hour time period.
So if you have a rock star on your list that is followed by numerous other Paper.li publishers, there is a high probability that they will headline as news, but not make it to your promo tweet.
If a twitter user requests not to be mentioned, we will blacklist them from our service.
If you want to increase the number of @mentions, try modifying and refining your sources.
The mentions shown in your paper settings are examples only.
*Situation (applies to manually sharing your paper using social sharing column on your paper)
If you are sharing your current edition via the social sharing column (see below) and occasionally not getting mentions, try to click less fast! Hovering over the twitter icon for just a few seconds allows us enough time to search for mentions. If you are too quick on the draw, we won't be able to fetch your contributors/mentions to include them.
For archived editions, there are no mentions automatically included since once a paper goes to the archives, we are no longer able to retrieve mentions.
Social sharing column on paper (left side)