The codes either doesn't work anymore or I'm not entering them right.
The codes are for the import/export deck function; they are different from reward codes. You must have a copy of the card referenced by the code in your inventory for the card code to work.
For example, if you type in 4sa into the Import/Export box in the Deckbuilding screen and press Import, then it will only work if you have a copy of Quantum Pillar in your inventory.