I cannot seem to get Workbench Plus powered. I have Solar Flux Reborn and Flux Network but Forge Energy will not power the workbench. I checked and it does power the Quarry Plus so I would assume it powers the others as well, just not the workbench.

Which version of Minecraft are you playing?

Workbench will start receiving energy after you selected recipe on machine GUI.
So place solar panel or adopter after selecting recipe.