Those flight times do not work for me and having a 15 hour layover in Dubai I would rather not have
Check with Emirates. You may be eligible for
Dubai Connect since you're there for over 8 hours.
what I find strange is if I do a dummy booking the flights that I want are available.
Do you know if your Economy tickets are a Special/Saver/Flexi etc? It may be that restrictions for those tickets apply.