Old player

So I've been away from the game for a long time now (2018/19), and decided to try to play again.
I've tried getting back into the game and play like I always used to but the game has changed WAY TOO MUCH.
I'm playing as a Mage and for some reason I can't heal myself anymore.
I found out that they've added a skill tree and I've put in points accordingly.
Even though I've unlocked the healing spell I can't heal.
I keep getting a message saying "Your mana bank is empty!".
Does anyone know how I can get past this wall that is a "mana bank"?

 

You appear to have gone down the arcanist archetype path. One of the perks removes your heal spell and replaces it with the mana bank, which fills up when you hit enemies with spells and can then be drained to give you more mana. You can think of it as a mana capacitor that slowly fills up and then can be drained to give you more mana.

 

You should read the abilities you pick because they can drastically change spell functions