I've had this problem for a while now and I absolutely cannot figure out why it's happening. I copied some code from Render#renderLivingLabel in the Minecraft source and it will not render no matter what I do, meaning nothing actually displays. I'm performing this render right after the entities do in RenderGlobal#renderEntities (which directly calls renderLivingLabel and it works) and the code is more or less exactly the same as when it is called.
update: i literally keep answering my own questions lol... Turns out Minecraft coordinates (at least in rendering) are wack and they actually have to be located at (x-renderPosX, y - renderPosY, z - renderPosZ)... I had done that at first but it was drawing weird so when I used a vanilla method I got confused