I have the same problem with a fresh install of Ubuntu 13.04 x64.
Software Centre says on the bottom of the Sync Between Computers page: 'To sync with another computer, chhoose "Sync between Computers" from that computer.' No other computers are listed.
The UbuntuOne app - Devices tab - lists all my pcs under my account, and files are syncing across all the machines.
From my Ubuntu One account on the web - My Account - Devices - I can see that the other machines - Ubuntu 11.04 to 12.10 - have logged in to sync but Ubuntu Software Centre on the 13.04 machine hasn't yet linked to Ubuntu One.
I have the same problem with a fresh install of Ubuntu 13.04 x64.
Software Centre says on the bottom of the Sync Between Computers page: 'To sync with another computer, chhoose "Sync between Computers" from that computer.' No other computers are listed.
The UbuntuOne app - Devices tab - lists all my pcs under my account, and files are syncing across all the machines.
From my Ubuntu One account on the web - My Account - Devices - I can see that the other machines - Ubuntu 11.04 to 12.10 - have logged in to sync but Ubuntu Software Centre on the 13.04 machine hasn't yet linked to Ubuntu One.