On wiki Christipedia templates cannot be openend anytime in the normal way with the Dutch word "Sjabloon". For instance, "https://www.christipedia.nl/wiki/Sjabloon:Onderwerpenregister" does exist, but cannot be found en opened. It is as if it does no longer exist.
However, if you replace "Sjabloon" in the URL with the English equivant word "Template", the page can sometimes (not always) be opened and edited.
So it seems to me the issue has something to do with the language setting and/or connecting to the server. Using a couple of times CTRL+F5 helps to be able to open "https://www.christipedia.nl/wiki/Sjabloon:Onderwerpenregister". Once opened, giving an ENTER to the same URL may lead to an empty new page as if the page not exist.
I checked the language setting under Preferences: it is Dutch, which is the right setting.