I made a coal generator x3 and a powercell multiblock. I did everything correctly including using the wrench to set input. The power is being taken, and stored. (Checked with mekanism power cube) but the Jade tooltip still shows 0 charge

I don't know Jade but is there actually no power in the multiblock? Can you verify that?

Also you forgot to mention the version

It's 1.16.5 there is power in it. Screen confirmed it. But the hover tooltip from jade/hwyla doesn't show any power inside

Then I guess it's a problem with those mods. My own mod The One Probe shows it correctly