Why am I getting a Oracle numeric or value error

I have a procedure that has 2 input paramaters to verify the username and password. I also have three 3 integer output parms to pass me back some info. Now I want to add a varchar2 value back as well giving me the first name of the user. The problem is I keep getting a numeric or value error and cannot figure out why. Can someone please shed some light on this for me? My code is attached.

PROCEDURE VerifyCounterparty(
    v_EmailAddress IN VARCHAR,
    v_Password     IN VARCHAR2,
    v_Count OUT NUMBER,
    v_AccountLocked OUT NUMBER,
    v_TradesCompanyId OUT NUMBER,
    v_FirstName OUT VARCHAR2)
IS
BEGIN
  SELECT COUNT(firstname) firstname,
    ACCOUNTLOCKED,
    TRADESCOMPANYID,
    FIRSTNAME
  INTO v_Count,
    v_AccountLocked,
    v_TradesCompanyId,
    v_FirstName
  FROM T_USER
  WHERE EMAILADDRESS = v_EmailAddress
  AND PASSWORD       = v_Password GROUP BY ACCOUNTLOCKED, TRADESCOMPANYID, FIRSTNAME;
EXCEPTION
WHEN NO_DATA_FOUND THEN
  v_Count           := 0;
  v_AccountLocked   := 0;
  v_TradesCompanyId := 0;
END VerifyCounterparty;

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