We recently fixed a rare bug which caused the auto close rules to not take effect.
Fixed: #611179 Ticket auto close rules set up under Configuration\E-mail Settings don't work and sometimes cause the Set State When User Replies setting under Configuration\Ticket Content not to be respected
I would recommend updating to the latest Lansweeper version (6.0.151.26).
If needed, you can find instructions here: https://www.lansweeper.com/kb/118/updating-your-installation.html