De acordo com este artigo :
In April 2014, Canonical announced that the cloud storage and synchronization features would be shut down at the end of July 31 of 2014, leaving the sign-on features intact.[4]
Parece que você precisa encontrar outros serviços de nuvem para backup.
O mesmo artigo lista outros serviços que podem lhe interessar:
The Ubuntu One service was similar to services such as Microsoft OneDrive, iCloud, Dropbox, Google Play Music, Amazon Cloud Player. Its client code was written in Python. It used Twisted for its low-level networking and Protocol Buffers for protocol description. Data was synced over a custom protocol called "u1storage", and stored on Amazon S3.[8]