You may have read the following on BoB:
"Please sign in on the login page to download books you have purchased. BooksOnBoard has temporarily stopped selling books. We are re-structuring to compete more effectively against Goliaths who have entered our marketplace since we first launched in 2006, i.e., Amazon, Apple, Google, Sony and Barnes & Noble."
According to Nate Hoffelder, there are some vendors that indicate BoB has not been paying their bills. That doesn't sound promising. As A3A said, do NOT delay in downloading your purchases. The window of opportunity could close...soon.