Android app from Amazon appstore not updating

Hi! I have a Plex app premium for android that I bought long time ago. However, I have noticed now that it does not seem to update, the version number on Google play and Amazon appstore are different. I also noticed that the app is not really searchable on the Amazon appstore. Any suggestions?

https://forums.plex.tv/t/plex-for-android/29115/last

Amazon may take longer to review new app versions than Google.

It is also possible, that older devices are no longer supported.