can´t assign a player to a token

One of my players is invisible to me, i can´t add him to any token as the program don´t recognize him inside the campaign.   (But he is, he can create topics inside the campaign just as normal).  So i kind don´t know what to do... i thinked of kicking one of my players (as i have 5 + 1 spectator) thinking removing 1 can help the program to fix itself but i would like to avoid that for now.  any ideas what can be causing the problem? 

Thiago, I want to confirm, has he ever entered the campaign itself? If he has not you cannot assign him tokens. The campaign is a separate system from the campaign details page.  - Gauss

Thx gauss. Maybe thats the problem, im going to try tomorrow and post here the results. 

It worked. Thanks for the help. 

NP Thiago :) - Gauss