I'm still having this same issue.
StartAllBack v3.9.3
Start11 opens when I use the Windows key, but if I click on the Start Menu icon on any monitor other than the primary monitor it opens the default menu.
Hello,
Sorry to hear you are having issues. How does you issue related to OP issue? Please create your own thread so we can help you there. Also, this might be conflict issue with StartAllBack. Please uninstall StartAllBack reboot and retest. Report back in your own new thread.
Thank you,
Basj,
Stardock Community Assistant.