CoC generates energy based on both a critical hit and that hit’s damage compared to enemy ailment threshold. If you don’t do enough damage, you don’t generate energy. Spell phys damage on your wand isn’t helping. You need to level your skill gems up to level 20. Your comet gem is currently level 11 and your character is 97. Your rathpith only having the 2 crit chance affixes, 1 of which is for mana that you don’t have, and neither of the damage affixes defeats the purpose of using it. You’d be better off with a non corrupted rathpith that still has damage per life, dreamer scepter, or rare focus with + spell levels on it. In your case, a focus with + levels is probably going to help the most.
Also, to be able to have comets raining down your life pool has to be around 150% or more of the life cost for comet for fast metabolism to keep up. With efficiency support on there that probably won’t be an issue for you but just in case you get your damage up and still only do one off comets and don’t know why