mana regeneration mastery

i have a mastery in phercia that says it regenerate 5 mana pr second but it does not work in poe 1

Show a screenshot of your mana regen in-game with and without it allocated. Most likely your 6L Flicker is costing way more mana than your regen.

Better solution if you want mana sustain with attacks is to use mana leech + instant leech mastery.