OK, this is painful.
I've stopped and unregistered the service, renamed the folder to c:\TNIResidentAgent (no spaces), re-installed and restarted the agent,
Now, the application attempts to download the update but just doesn't do it - no log entries, nothing to diagnose from - just this in the log file:
2017.09.12 21:17:54:010 Starting service...
2017.09.12 21:20:02:286 Scheduler: downloaded new settings
2017.09.12 21:25:02:260 Scheduler: starting scan...
..but nothing downloads
Help!!!