Hard Disk Monitoring

I'm a new registered user. My PC had 4 drives: 1) C: a 1TB SSD, 2) D: a 2TB HDD, 3) E: another 2TB HDD, and G: a 1TB external HDD. When I first installed HDS all 4 drives showed their temps in my Windows system tray. The next time I booted up my computer, only the C:, E:, and G: drives showed up. I can't figure out how to get the D: drive to display it's temp icon again. Any help would be appreciated.
Thank you for your response.

Please check Configuration -> Hard Disk Drives page.
There it is possible to enable/disable tray icon(s) for all disk drives: by DOUBLE CLICK on any drive, it is possible to toggle if a drive should have associated tray icon displayed.
By default, all drives have icons - if they provide temperature value.

Please note that sometimes Windows may hide one or more icons - so it is possible that Hard Disk Sentinel attempt to show it - but depending on the system settings, only fewer icons displayed.

Thank you for your patience, and for your concise response. It is greatly appreciated.