According to local media, Addison was supposed to report to training last week alongside fellow trialist Jason Banton.
The former Derby County man, however, did not show up, and the reasons for the absence remain unclear.
Addison, who was recently let go by Peterborough United, has also been on trial at Southend United and Hamilton, but neither club has offered him a permanent deal.
What do you make of this story? Let Pride of Nottingham know by signing up to the site, visiting the forum and joining the conversation.