I was advised to report it as a bug here. I have latest Qubes version 4.2.1. but this issue was on previous versions too. Sdwdate sometimes doesn’t start on some qubes. It always works on sys-whonix but sometimes fails on some app qubes. This is how it looks like:
It has two conditions of failure and they never happen at the same work session. Only one of them.
Condition 1: sdwdate didn’t start on single app qube and sdwdate icon of this qube didn’t appear in Time Synchronization Monitor. To fix this I have to restart qube.
Condition 2: sdwdate did start with app qube but after some time its icon (sdwdate icon of that single qube) disappears from Time Synchronization Monitor and I make conclusion that sdwdate on this qube shut down. So I again have to restart qube to make it work.
P.S. It may be important so I want to mention that Qubes installed on HDD disk so it may be somehow related to this issue.