keyboard shortcuts not working, greyed out in menus

This afternoon suddenly all keyboard shortcuts except CMD-C stopped working in all applications, all menu entries for shortcuts are greyed out in all menus. All commands work when selected in menus.

Is there a Terminal-command to switch them back on?

If not: What can I do regarding diagnistics?

Thanks!This afternoon suddenly all keyboard shortcuts except CMD-C stopped working in all applications, all menu entries for shortcuts are greyed out in all menus. All commands work when selected in menus.

Is there a Terminal-command to switch them back on?

If not: What can I do regarding diagnistics?

Thanks!

macOS 11.6 (20G165) · MacMini (M1, 2020)