It certainly looks like the logs are being successfully processed.
Do you receive other emails from OJS to the email listed as the principal contact in your Site Administration -> Site Settings? If so, is there any spam filter that could be capturing the error messages? The subject line will look something like "Usage statistics file loader task - 5446ebc83d9b1 - Error".
Are you familiar with access to mysql? If so, you can look at the "metrics" table in the database. You should see multiple rows for each "load_id", where "load_id" is the filename that now appears in usageStats/archive. If no rows exist for the filename, but no error appears, my best guess would be a mismatched base_url. For example, if your config.inc.php says your URL is http://myjournal.tld
, but access generally actually happens via http://www.myjournal.tld
, then this access will be missed. For more information about this issue, see the conversation here: viewtopic.php?f=8&t=13404&p=51618&hilit=base_url#p51618