Did you ever find out what is causing this?? I am having the same problem. it worked last night. Earned over $300 for one post. I just signed up last night. Now though I am getting the same error. I will wait overnight and see if maybe we just have to wait for the voting power to come back. That may be what is going on. Steem just underwent a hardfork so people can only vote 10 times at max voting power but the votes are worth more. So it is a tradeoff. Keep me updated will you? I will do the same.