Only in the hope that it helps, not to pester, I'm having the same issue in Version 6.8.3 2020-03-05. I can see the temperature for my nvme disk on the tower/Dashboard page in the "Unassigned" widget (bottom right for me), but not on tower/Main in the Unassigned Devices section. Just get an asterisk there.
I'm fairly confident that it happened on the update today, because I just installed a new fan earlier this afternoon and have been paying a lot of attention to the temperature in the hope of solving an entirely different problem. So I saw (and was watching) the temperature right before the update on the Main page.
Hope that helps. Thank you.