Is it the option "Refresh Files" in the Help tab?
You can manually click Help > "Refresh files" as you mentioned (this will refresh all console data files, not just the definitions), or you can click Tools > Options > Downloads and click your scheduled download in "Scheduled automatic downloads" section and click "Run now" (make sure you actually select the job, or "Run now" won't do anything). If there is no longer a job scheduled to download "Core engines/definitions" go ahead and click Add to create the job again.
If the job is still there, I would strongly recommend checking View > Event History and look for events titled "Core engines/definitions download" to see what's happening. You should see any errors listed there, then be able to troubleshoot the issue preventing the automatic update.
We're certainly here to help if you need any assistance with that troubleshooting, so go ahead and open a case if you need help digging into that.