Hello Everyone,
I recently got a QM achille used, and after a month of usage , yesterday when I was going to steam milk I saw boiler pressure gone to 0.5-0.6 and it kept on decreasing. Before this i had pulled a shot and made a latte too and it was fine. I turned off and turned on the machine but the pump works to pull water from reservoir , the light of heating element is on but doesnt seem that it is heating.
I have never opened this machine up before so would like to know from you good folks next steps.

I would 1st suggest downloading the manual of your machine including an exploded parts diagram and wiring diagram so you could begin to understand how things are connected and supposed to work.

With the machine unplugged, open it up and look for things such as connector plugs that might be loose, burnt or otherwise defective. Check any resettable (red) circuit breakers. Take pictures for reference and posting.

Do you own a digital multimeter?

It might be less complicated than you think. Post back with your findings and observations.