I can’t get sidebars to work at all. I mean, Main shows up along the side of my screen, but if I click a tab that has a different sidebar assigned, nothing changes.
Hard to say.
Assuming you have restarted with no affect, I would be tempted to run the Reset command.
Maybe click Save Setting for Support so you have that if we need it.
Resetting toolbars did nothing, but I reset everything and that fixed it.