I was having this issue as well. I rebooted my modem, my roku. Uninstalled and reinstalled the Viki app. It did eventually did load but it took a lot longer than usual. Several minutes.
I received an email from Viki Community Support and ticket number, says they're looking into the problem. Status is still "open". I hope I get another email when the problem is resolved.
I started having this problem as well. I uninstalled, updated, added the vikiglobaltv on my roku account and still I get kicked out whenever I try linking the login code to my roku. I can get on ...