what wallet version are you using? Make sure its 0.3 (check
website) . Also some AV or firewall software may block it from sync. Also what language of the seed?
It was the latest version of the wallet that I downloaded the very same day.
I have no 3rd part AV or FW.
I was trying to restore seed from sumo, language of the seed is russian.
Anyway lately I managed to restore directly from sumo wallet.