问题可能出在规则B的设置上。需要检查以下几点：

1. 检查规则B的主题过滤器是否正确。该过滤器应该与函数的主题匹配。
2. 检查规则B的操作是否是“调用Lambda函数”。如果不是，请修改为相应的操作。
3. 检查规则B是否在正确的规则集中。如果不是，请将规则添加到正确的规则集中。
4. 检查Lambda函数的权限。确保Lambda函数具有执行AWS IoT规则所需的权限。

以下是一个示例代码，它演示了如何设置AWS IoT规则来触发Lambda函数：

const AWS = require('aws-sdk');
const iot = new AWS.Iot();
const lambda = new AWS.Lambda();

exports.handler = async (event, context) => {
    const ruleNameA = "myRuleA";
    const ruleNameB = "myRuleB";
    const functionName = "myLambdaFunction";

    // Create rule A
    const ruleA = await iot.createTopicRule({
        ruleName: ruleNameA,
        topicRulePayload: {
            sql: "SELECT * FROM 'my/topic/a'",
            actions: [
                {
                    lambda: {
                        functionArn: `arn:aws:lambda:${process.env.AWS_REGION}:${process.env.AWS_ACCOUNT_ID}:function:${functionName}`
                    }
                }
            ]
        }
    }).promise();

    // Create rule B
    const ruleB = await iot.createTopicRule({
        ruleName: ruleNameB,
        topicRulePayload: {
            sql: "SELECT * FROM 'my/topic/b'",
            actions: [
                {
                    lambda: {
                        functionArn: `arn:aws:lambda:${process.env.AWS_REGION}:${process.env.AWS_ACCOUNT_ID}:function:${functionName}`
                    }
                }
            ]
        }
    }).promise();

    console.log(`Created rules: ${ruleA.ruleArn}, ${ruleB.ruleArn}`);

    return {
        statusCode: 200,
        body: