How to fix this Permalink Problem

I'm havinga a small but annoying issue regarding permalinks (I'm using multisite+domainmapping).
Basically i have this site
that until today was not using pretty permalinks if I try to activate it my home page gives me 404 and the url becomes like this:
all the website continue to work as expected though
this is happening only if I visit the main URL

I've granted access already :slight_smile: