Before the first week of the Colvis experiment, all newly created characters are marked "inactive". Up to 5 characters per participant will then be turned "active" for the experiment.
The reason behind this choice is the risk that the visualization does not efficiently scale to more than a few hundred characters. While there are solutions to this problem, we are yet to implement them.
If you want to see the inactive characters in the graph, you can however switch on the "See inactive characters" option in the visualization's settings.