Calendar isn't visible when I start the app, but it's there

Since I upgraded to Sequoia, whenever I start my Calendar app on my Macbook, it defaults to showing only the US Holidays selection from the Other list in the left pane. The calendar is there, and when I go up and select the Windows tab, then scroll down and select Calendar, it shows up and everything is normal. But why isn't is showing up by default, like it used to? I've checked all the Settings, and they are all correct. It has to be a bug in Sequoia, right?