I think there is a conflict between “Domain Mapping” and Pro-sits, or something like that.
My multisite did not create new pro-sites (it was processing for ever – see screenshot). I went throw the process of deactivating all the plugins and reactivating and Domain Mapping is the undisputable Winner.
It is deactivated now and all works fine, and I can live without it for now but will be nice to have it working.
Please let me know if you find or need anything.