I am also experiencing this issue, may I add that it appears the root cause is when you have Start11 > Taskbar > Enhanced taskbar settings > "Enable Start11 autohide mode" enabled and Start11 > Start Menu > Configuration > Advanced Options > "Use fullscreen menu" both enabled.
When both the above settings are enabled it "pushes the top of the start menu" off the viewable screen area and you are then unable to see the header of the icon group. The titles are still there, as if you disable "Use fullscreen menu" they are visible once again.
I am using:
Windows11 23H2
Start11 v2.08
Style: Windows 10
2No. LG 27GN800-B Monitors
I have tried other options such as disabling "more tiles" etc, however it appears to only be a conflict between the 2 detailed above. When I hit the Windows key it looks like the Start11 background process is to calculate the fullscreen size of the start menu first (with no taskbar visible), then applying the taskbar as visible after, which is in turn pushing the top of the full screen start menu off the top of the visible screen real estate and therefore making the group name(s) not visible.
The same issue occurs if the start menu is opened on my primary and/or secondary monitor.
I have disabled "Enable Start11 autohide mode" for now, but would like to use both settings together if a fix can be found for this conflict.
I would guess perhaps the "Enable Start11 autohide mode" advanced setting was removed when SirBedwyr uninstalled and reinstalled Start11 and therefore the issue did not present itself again. If other users are able to test and confirm?
Hope this helps to troubleshoot the issue, your assistance is appreciated.