There could be several reasons why you are unable to perform a balance transfer on your Citi Card. First, ensure your account is in good standing, as past due payments or exceeding your credit limit can cause issues. Secondly, check if your card is eligible for balance transfers, as some Citi cards might not offer this feature. Additionally, there may be a limit to the amount you can transfer, which could prevent the transaction if it exceeds this limit. Lastly, ensure you have not reached the maximum number of balance transfers allowed within a specific period as defined by Citi’s terms and conditions.