Sorry about that last blog post folks.
False Alarm
Turns out Arq 1.3.14 works fine. A customer had reported that his backups were gone right after he updated, and I thought I reproduced the problem, but it turns out I didn’t reproduce the problem, and furthermore it wasn’t actually a problem!
The customer had pushed the “Change Region” button in the Advanced section of the Preferences, and had chosen a different S3 region. When you choose a different region, Arq actually has to create a different S3 “bucket” (you can’t move an S3 bucket from one region to another). Arq doesn’t copy the configuration and data to the new bucket. It even says so on the “Change Region” dialog:

After a lot of emails back and forth I finally figured out that’s what happened. He neglected to mention that he had changed his S3 region.
My initial reaction was that this was a data-loss bug, and others should be warned so that others can avoid data loss. I’m not sure if I reacted correctly in this situation, and I apologize for the false alarm. I guess I need to relax and get all the facts before announcing to everybody that there’s a problem!
Arq 1.3.15
Another customer did uncover a legitimate bug however: in “30-day trial” mode, Arq acted as if the trial was expired, whether it was past 30 days or not.
Arq 1.3.15 fixes that bug.
Pick “Check for Updates” from the Arq menu to automatically update to 1.3.15, or download it from the web.