Ok so I called them and they gave me some interesting information. Apparently the reason Jakarta does not appear as a bookable option on the website is due to a large amount of fraudulent activity. I wonder if there are other destinations like this. I hear Lagos and Mogadishu are nice this time of year.
Anyway, she informed that flights and hotels to/in Jakarta can be booked over the phone. In the case of hotels she said to research a few options and then they will check with their providers to see if those options are available.
I also gave her feedback saying that it would be nice to have an indication to call to book Jakarta rather than the current setup which just makes it look like the website is broken or that Jakarta does not exist. She said she'll pass it on but "they do not get many requests to book Jakarta".