I looked into this problem. The plugin won’t work on any non-english version of krita as authors use text that is translated to get access to docker. The program is looking for Tool Options but it is something else in your version.
I printed out the French actions in there getting:
Afficheur de journaux
Animation
Bibliothèques vectorielles
Boîte à outils
Calques
Canaux
Compositions
Courbes d'animation
Documents récents
Ensembles de tâches
Gamut Masks
Gestion des LUT
Gestionnaire de bande dessinée
Grille et Guides
Histogramme
Historique d'annulations
Historique de préréglage de brosse
Motifs
Organiser
Outil numérique de mélange des couleurs
Palette
Panneau tactile
Pelure d'oignon
Préférences d'outils
Préréglages des brosses
Quick Settings Docker
Sketchbook Manager
Snapshot Docker
Sélecteur de couleurs artistiques
Sélecteur de couleurs avancé
Sélecteur de couleurs particulier
Sélecteur de couleurs simplifié
Timeline
Vue d'ensemble
Préférences d'outils looked a lot like some sort of options 
(google translator also said so), so I checked it and managed to open it with french translation.
I couldn’t find a neat way to differentiate those actions other than this text (and they are organized in alphabetical order, so I can’t pick the right one, as the position depend on translation), but I hope @slightlyangrydodo or @Kapyia will do 
If you want to fix that until then, you can got to the folder where the plugin is stored (Settings > Manage Resources > Open resource folder, and then pykrita > krita-redesign > nuTools > nttooloptions.py) and change the line 50 to:
self.dockerAction = self.findDockerAction(window, "Préférences d'outils")
or to those two lines:
self.dockerAction = self.findDockerAction(window, "Tool Options")
if not self.dockerAction: self.dockerAction = self.findDockerAction(window, "Préférences d'outils")
if you want it to work both in english and french version 
Oh, and I believe that this text is normally displayed over the Tool Options docker, so you can simply use this name for any language you like