The Cinnamon power management settings on Mint have options to suspend OR lock my ThinkPad when the lid is closed but I can’t seem to find a way to make it do both.
Update: fixed
The Cinnamon power management settings on Mint have options to suspend OR lock my ThinkPad when the lid is closed but I can’t seem to find a way to make it do both.
Update: fixed
Something is actually preventing the system from being locked at all. If I click the lock icon in the menu above the log out button, nothing happens.
Do you have a screenlocker program installed and setup?
A quick search tells me that
cinnamon-screensaveris its name for Cinnamon.Perhaps you can also run
journalctl -fin a terminal and then click the lock button in the menu, to see if there is any error related to that at that moment.cinnamon-screensaver/zara,now 6.4.1+zara amd64 [installed]

I don’t see any errors at all.
Dec 08 23:17:01 Mint-Yoga CRON[10491]: (root) CMD (cd / && run-parts --report /etc/cron.hourly)
Dec 08 23:17:01 Mint-Yoga CRON[10490]: pam_unix(cron:session): session closed for user root
Dec 08 23:17:18 Mint-Yoga dbus-daemon[780]: [system] Activating via systemd: service name=‘org.freedesktop.hostname1’ unit=‘dbus-org.freedesktop.hostname1.service’ requested by ‘:1.190’ (uid=1000 pid=10482 comm=“/usr/bin/gnome-screenshot --gapplication-service” label=“unconfined”)
Dec 08 23:17:18 Mint-Yoga systemd[1]: Starting systemd-hostnamed.service - Hostname Service…
Dec 08 23:17:18 Mint-Yoga dbus-daemon[780]: [system] Successfully activated service ‘org.freedesktop.hostname1’
Dec 08 23:17:18 Mint-Yoga systemd[1]: Started systemd-hostnamed.service - Hostname Service.
Dec 08 23:17:51 Mint-Yoga systemd-resolved[723]: Clock change detected. Flushing caches.
Dec 08 23:17:51 Mint-Yoga systemd-timesyncd[733]: Contacted time server 185.125.190.57:123 (ntp.ubuntu.com).
Dec 08 23:17:51 Mint-Yoga systemd[1]: apt-daily.service - Daily apt download activities was skipped because of an unmet condition check (ConditionACPower=true).
Dec 08 23:18:09 Mint-Yoga systemd[1]: systemd-hostnamed.service: Deactivated successfully.
Yeah, nothing seems related to locking the screen.
Perhaps try some cinnamon related place and they might know how to get the related info (I haven’t used cinnamon).
Update: I installed xfce, which is also broken in its own way, but it allowed me to reinstall Cinnamon which now allows me to lock the laptop, manually or automatically.