Error Code 1241. Operand should contain 1 column (s) function MYSQL

Create a function in mysql to work with a sequence the code of the function is as follows:

FUNCTION 'fn_nextValue'(SEQNAME varchar(50)) RETURNS bigint(20)
BEGIN

DECLARE EXIST_SEQ INT;
DECLARE CUR_VALUE BIGINT(20);

SET EXIST_SEQ = (SELECT COUNT(1) FROM bd_triggers.secuencias WHERE nombreSecuencia = SEQNAME);

IF EXIST_SEQ > 0 THEN
    UPDATE bd_triggers.secuencias
    SET secuenciaValor = ((IFNULL(secuenciaValor,0) + secuenciaIncremento) < secuenciaMaximo,
                            IFNULL(secuenciaValor,0) + secuenciaIncremento,
                            secuenciaMaximo);
END IF;

SET CUR_VALUE = (SELECT secuenciaValor FROM bd_triggers.secuencias WHERE nombreSecuencia = SEQNAME); 
RETURN CUR_VALUE;
END

For the sequence table which has the following structure:

A record already exists in my sequence table:

SEQ_ID  |1  |1  |18446744073709551615   |NULL

But when trying to call the function:

SELECT bd_triggers.fn_nextValue ('SEQ_ID');

This error marks me:

Error Code 1241. Operand should contain 1 column(s)

If you could tell me where I made the mistake to correct it, they would help me a lot.