Glossify filter not available for input formats

Hi,
I've installed Glossify and simplehtmldom on a Drupal 6 instance,
after that, I've been able to go to admin/settings/glossify and to setup how I wanted Glossify to work.
But when I go to the input format list (admin/settings/filters), then to the config of one format, I can't see any "Glossify" filter added among the other filters I have.

And as you can expect : nothing is "glossified" in my contents since I've not been able to activate the glossify filter ...

I don't have any error message displayed on screen nor recorded in the db log, so I have no idea of what's going wrong ...

Any help would be greatly appreciated,

Thanks

Hervé