It happened to me too, they sometimes disable the "Send to my BTC balance" button maybe manually maybe automatically but normally within few days they fix it, check their signature campaign thread and you will see that you are not the first one facing this 'bug'
Yes. Some people say that this happen because they are refilling their balance to pay members. And they don't like people posting about that on the thread... It's a very knowed issue. Continue working and your satoshi will be paid when the button back to the normal.
Maybe that could be a reason too, to refill the balance but if anyone has any issue it better to send them a ticket and/or try to reach any moderator on their chat.