Redeeming a referral code a friend has shared with you is a straightforward way to get yourself credits.
However, there are some restrictions on referral code redemptions:
You can only be referred once.
You cannot redeem a referral code if you benefit from a membership discount.
You cannot redeem a referral code if you have already redeemed a referral code on any account on your device.
If none of these restrictions applies to you but you still can't redeem a referral code, feel free to get in touch!