Same problem happened to me.
Once on 0.9.21 I believe, several of the common hotkeys (Ctrl - O, Ctrl - P, navigate back/forward) didn’t work anymore. Restarting Obsidian fixed the issue.
Today on 0.9.22 the custom hotkey I made for open today’s note didn’t work anymore. I use Ctrl - N for that hotkey, but instead got the standard ‘make new note’ behaviour that is the default for Ctrl - N. Looking in the hotkey settings I also couldn’t find the ‘go to daily note’ hotkey anymore. When I restarted Obsidian, the hotkey worked fine again.
I’m on Windows.