Originally Posted by bluegt

I did a search for a few dates about ~1 month out in the mobile app and I am seeing availability. Perhaps provide your dates?

If I am having that sort of issue I will do a search in other cabins and if nothing is showing, give them a call or drop an email so they can investigate. I've experienced a lot of strange booking issues with US-bound flights... (as best I can tell, SIA is forgetting to open up availability on some dates/routes...)