Hi!
The custom taxonomy term class is programatically limited to 50 terms per taxonomy. You can unlock this limit by opening the \ajax-search-pro\backend\settings\class\customtaxonomyterm.class.php and go to line 110 where you should see this:
[php]$terms[$taxonomy] = array_slice($terms[$taxonomy], 0, 50, true);[/php]
change that to:
[php]$terms[$taxonomy] = array_slice($terms[$taxonomy], 0, 500, true);[/php]
and it should show ever category now.