I tried to address this in the cloud sync forum, but it appears that it has been locked. It looks like a ton of people have had this problem, but last responses are from back in March and I can’t see where anyone figured it out.
I have Plex Pass and Amazon Drive (per the Plex recommendation as the best working option). My movies transcode fine, but then get stuck forever (weeks) in “Waiting to Upload”.
This feature is the only reason I paid to upgrade to Plex Pass and the only reason I paid for an Amazon account. Has anyone had this problem and fixed it?
As stated above by @amccook there have been a number of issues with Cloud Sync. Specifically with Amazon Cloud.
Also dont get confused with Plex Cloud and Cloud Sync, they are 2 different things. I am not aware of Amazon being recommended as best provider for Cloud Sync.