I would ignore the 8-9 time, check ins rarely start earlier than 1030 as they have to get all the people from the previous sailing off the ship before they can start your check in/sailling. More specific time will show up later once you are allowed to do online check in.
That's frustrating! Could be a few reasons - if your sailing is still very far out, it could be that it's just not actually available for purchase yet. It could also just be a glitch and you need to try again later. It may also mean that a bunch of people hopped on it quick and it is already sold out for your trip.