@octothorpe if you manually use the macOS lock combo of control+command+Q does this lock your Mac?   If so, try quitting Alfred, then removing him from the macOS Security & Privacy > Privacy > Accessibility preferences, and re-adding him back again. If there is an underlying mismatch in the macOS privacy prefs, Alfred may have been blocked from simulating a lock.   If this combo doesn't work, then you can check what combo is expected under the Apple logo in the top