Wherever possible, StoragePoint surfaces error messages returned by HCP/HCAP either directly to the user or within the SharePoint ULS logs. You should refer to your HCP/HCAP documentation for errors logged by the HCP/HCAP Adapter.
For event based retention to work, the item has to exist before it can be tagged with retention during the archive process. So if content is uploaded with a change to the metadata that would normally archive the item, it wont be archived. However, any subsequent change to the item will flag it for archiving, and the next successful run of the content queue migrator will archive that content.