I'm having the following situation today:
1) There was a power outage at one of my clients
2) We shut down proxmox gracefully by:
qm suspend 104 --todisk 1; shutdown -h now
3) Then we rebooting the machine, the VM did not start:

4) With no better idea, I read it on this forum that I need to manually unlock the VM with the following command:
qm unlock 104
which I did.
5) After that, we were able to start the machine but I wasn't able to connect to the console:

I'm answering my own question and I also think that this is probably a bug, this is what I needed to do:
We needed to click "Resume" on the VM after I clicked "Start", I'm not sure whether this is right (probably not) but it took me some time to figure it out.
With 1) start and then 2) resume it's working:

1) There was a power outage at one of my clients
2) We shut down proxmox gracefully by:
qm suspend 104 --todisk 1; shutdown -h now
3) Then we rebooting the machine, the VM did not start:

4) With no better idea, I read it on this forum that I need to manually unlock the VM with the following command:
qm unlock 104
which I did.
5) After that, we were able to start the machine but I wasn't able to connect to the console:

I'm answering my own question and I also think that this is probably a bug, this is what I needed to do:
We needed to click "Resume" on the VM after I clicked "Start", I'm not sure whether this is right (probably not) but it took me some time to figure it out.
With 1) start and then 2) resume it's working:
