@NineMile I just tried this with DWC/RRF 3.5.2, toggled the 'Do not close error message automatically' to off, then provoked an error that displayed a red box. Like when a blue or green message box pops up, the red box had a white progress bar at the top of it, and disappeared once that completed. Also tried changing the notification period, and that worked too.
I've noticed a couple of people have had problems with their DWC settings. Refreshing these seems to resolve some issues. Whether this is because the format of the dwc-settings.json has changed over time, or the file has become corrupt and not writeable, I'm not sure. Try renaming sys/dwc-settings.json to something different (eg .old on the end), and refresh the browser. Edit something, eg set 'Do not close error message automatically' to off, to create a new dwc-settings.json, and see if that resolves the problem.
Ian