Can't login in admin

[pchulpleusden]

I've contacted my hosting and he says that he has never seen such a problem before, so that isn't very useful. Meanwhile I've made another GetSimple-directory with a whole new installation on it and the strange thing is that this works perfectly! What I can do is transfer all the data from the old installation to the new one en hope it works or maybe you have other suggestions?

I must say that I have one little health warning:
ZipArchive Not Installed - Warning

But I think that this doesn't have anything to do with my problems, does it?

Thanks!