If you are using Amazon AWS S3 file archive plugin, the file contents are stored in S3 in a tree structure like so:
{bucket_name} / {database_name} / {file_id}
If you move your installation or even just change the database name, the files backed up from the previous installation will not be accessible on the new installation because the application looks for them at the new location in a folder named same as the new database name.
What you can do to fix this is move the files within the S3 bucket from folder {old_database_name} to folder {current_database_name} using aws-cli mv command.