I think you were using a very, very early beta on that. The builds with the support were not official beta builds, and were not released on the Play Store or Amazon store. I believe they were 9.6.0.xxxx numbered at first, but that changed during that development work.
The only official beta builds that have the support active were released just yesterday and they have version numbers of 9.7.0.xxxx. If you were using one of the earlier builds with ASS support you want to upgrade to the current (official) beta release because of all the improvements. Here’s the post:
And there’s even been one newer beta release already for a crash fix.
ASS subtitle support is not in the stable release yet so it’s not going to be on the Amazon App store version.
