There is a setting under the "My Preferences" section that can be used to set the "autocomplete" feature which further auto-populates options for you in the Search bar.
This can be toggled with a keyboard shortcut so you may have accidentally turned it off. Use <Esc> or <Alt> <Space> to toggle it.
Please navigate to your 'Account' > 'Preferences' page and check if the autocomplete feature is enabled.
Our documentation for reference on this page is here: Preferences Page