Creating an Essentia storage cell, and placing it in an ME chest does not allow input or output of essentia.

When putting a storage cell with Essentia already in it, in the chest, the interface does not show any contents. I tried putting an Essentia Terminal on the chest, and still is shows no stored essentia and allows no adding of essentia.

Try powering the chest with AE energy (not just RF energy as it seems to only want 80/80 RF).
When I did that, the top of the chest shows the essentia contents and lets me add/remove essentia.

This is still a bug IMO, but the workaround is effective for some uses.

I swapped the TE Hardened energy cell for an AE2 Creative energy cell and that seemed to work. I'm playing Blightfall Mod pack, and have no way to generate AE2 power reliably or efficiently, but it is interesting that this experiment worked.

I thought maybe this is an issue with the ME chest, but I tried a normal storage cell and that works just fine on RF.

Weird. I wouldn't expect the source of power to have any bearing on if the cell works or not, unless its simply not getting enough power. Does a creative TE cell work?

Did some testing. A TE Creative energy cell does not work either.

If I pass the RF though an energy accepter to the chest it does work. But I guess that kind of makes sense as the accepter is turning RF into AE.

It's still odd that the chest will work with direct RF and a normal storage cell, but not an essentia one.