As mentioned in other answers, in MacOS there's a conflicting shortcut that uses Shift-Command-A set at the system level by default that you can disable.

In MacOS Sequoia (15.x.x), you can find it under Keyboard Settings within the System Settings app.

Steps

1. System Settings > Keyboard > Keyboard Shorcuts...
2. Click "Services" Tab inside left sidebar
3. Expand the "Text" grouping within the list of shortcuts
4. Uncheck "Search man Page Index in Terminal" (or change the keyboard shortcut)

Screen recording of accessing keyboard shortcut setting "Search man Page Index In Terminal" within MacOS Sequoia 15.3.1's System Settings app