Thanks for the screenshot. I was looking in the wrong place (system settings -> accounts). However, I really think that I had tried this button, with no effect (but I can’t test this anymore), so forget it.
Anyway, the current label in French does not have exactly the same meaning:In this screenshot it is “adressbücher neu erkennen” which I suppose could be translated by “discover new address books” (it is a guess based on what I found in online translators) in French it is “Actualiser le carnet d’adresses” which would be literally translated by “update address book”.
I am using DAVx5 22.214.171.124-ose(267). So I joined Transifex to check the translations, and indeed, the German translation has the good meaning. I just updated the French translation to fix this issue (strings 103 and 105):Refresh address book list -> Actualiser la liste des carnets d’adresses Refresh calendar list -> Actualiser la liste des calendriers