If the key that keys into QSS has a preferences set:
and QSS requests to apply a high contrast theme:
Note that the high contrast theme is not an existing preference in the user's preferences set.
In this case, Lifecycle Manager is not able to apply high contrast theme.
The cause of the problem is, for the security reason, the matchmaking for applying user preferences only returns the filtered result on solution registry and inferred configurations etc for preferences that are already in the user's preferences set. Using this result is not enough to handle any request change on new preferences.
The solution is, when receiving a prefs update, a local matchmaking should be performed to accommodate new preferences.