Maybe the English language localization team needs a new member. What even is the primary language of this game? Québécois?
Another update will come shortly.
What would be the proper english version?
“We are currently doing maintenance”, or even better, “We are currently performing maintenance”.
Of course, this is a game where a card deals damage to a creature equal to it is power, and another card puts a creature on top of it is owner’s library.
Sorry, I should have clarified for non-native speakers. Nouns in English come in two types: “countable” and “uncountable”. Countable nouns include things like, "card, “creature,” or “token,” to use some MtG examples. Uncountable nouns include things like “water,” “happiness,” and “maintenance.” (Also “life” and “power” in the way they are used in this game.) Uncountable nouns never have the words “a” or “an” in front of them. To a native speaker it just sounds weird; what is “a water”?
Intersting…I do know (and thought to understand) the concept, but I considered it to be correct ( since “maintenance” appeared to me as countable I wasn’t able to find the mistake: in my mother tongue it’s almost exclusively used as a plural, making the differentiation way more complicated )
Thanks for taking the time!
Don’t even get me started on the unacceptably shoddy grammar in this game. To provide another example, one of the most pervasive mistakes is the incorrect use of “less” where it should be “fewer.” It’s in just about every objective!
damn, look at us getting some free schooling here. Appreciated 
[edit] Can’t embed images?
Yeah. This is why I shouldn’t have been surprised at the mistake in the maintenance message. It’s clear whoever writes the text for this game doesn’t understand the countable/uncountable distinction.