Hi, I started the mod-pack few days ago, so with last update.
I didn't manage to make mini-boilers producing steam. I can see they're plenty full of water but the third buffer stays empty.
I've tried to attach the mini-boiler to a melter, to an ember activator fully running but no result

Odds are you have the boiler attached to the top of the machine. It needs to be attached to the bottom block on the side

I've tried the bottom and top both

oh... OK I didn't tried the bottom block of the melter.. my bad.
It works. thanks a lot. Sorry for bothering.