Change language from French to English for Exact Online add-in Invantive Control for Excel

In Invantive Control for Excel on Exact Online, I get all text and messages in French as for example:

Une erreur s'est produite lors de la validation du modele de donnees de base avec version 15 des specifications referentielles.

Also, the Invantive buttons in the ribbon are in French, whereas the normal Excel buttons are in Dutch, as shown below:

The Exact Online model was developed in a Dutch environment which produces readable text.

How do I get the language of the errors and the buttons changed to Dutch or English?

The language used specifically for the Invantive buttons is coming from the language chosen in Exact Online by the current user.

When multiple data containers are active next to Exact Online, the language is determined by the first data container that answers the question for the preferred language code of the connected user. This is in general the one with the lowest order in settings.xml.

To get both Excel, Invantive Control and the Exact Online model to use the same language: set your language in Exact Online to the language of your Office installation.

Please note that you may still see differences; when the Windows language is different from the Office language some controls like the 'OK' button in Office will use the Windows language whereas others will use the Ofice language.