1. 确保您已正确设置了SFTP连接并将其添加到List SFTP Processor中，并且您具有正确的文件系统权限。

2. 检查您的List SFTP Processor是否有正确的文件过滤器设置。

3. 尝试升级您的Apache Nifi版本，因为某些旧版本可能存在该问题。

4. 检查您的操作系统、Java和Apache Nifi的日志，确定是否存在任何错误或异常。

5. 尝试使用其他SFTP工具，例如WinSCP或FileZilla，检查能否从该SFTP连接下载文件。

下面是Python代码示例，使用Apache Nifi API来列出指定目录中的SFTP文件。

import nipyapi
from nipyapi import canvas, nifi
from pprint import pprint

# 获取Apache Nifi API参数
nipyapi.config.nifi_config.host = 'http://localhost:8080/nifi-api'
nipyapi.config.registry_config.verify_ssl = False

# 获取认证令牌
credentials = nifi.UserCredentialsDto()
credentials.username = 'admin'
credentials.password = 'admin'

# 您的SFTP连接配置
sftp_connection = nifi.SFTPListingRequestDTO()
sftp_connection.host = '192.168.0.100'
sftp_connection.port = 22
sftp_connection.username = 'user'
sftp_connection.password = 'password'
sftp_connection.remote_path = '/example/path'

# 用ListSFTPProcessor列出SFTP目录中的文件
processor_fqn = 'org.apache.nifi.processors.sftp.ListSFTP'
processor_name = 'ListSFTP'
processor_loc = nipyapi.canvas.get_process_group('My Process Group').id
processor = canvas.create_processor(
    parent_pg=processor_loc,
    processor=nifi.ProcessorConfigDTO(
        type=processor_fqn,
        name=processor_name,
        position=nifi.PositionDTO(x=400.0, y=400.0)
    )
)
canvas.set_processor_relationships(
    processor,
    {
        'success': ((processor, 'success'),),
        'failure': ((processor, 'failure'),)
    }
)
canvas.update_processor(
    processor,
    nifi.ProcessorConfigDTO(
        id=processor.id,
        properties={
            'Remote Host': sftp_connection.host,
            'Remote Port': sftp_connection.port,
            'Username': sftp_connection.username,
            'Password': sftp_connection.password,
            'Remote Path': sftp_connection.remote_path,
            'File Filter': '',
            'Query Interval': '5 sec',
            'Minimum File Age': '0 sec',
            'Maximum File Age': '0 sec',
            'Ignore Dotted Files': 'true',
            'Recursive Search': 'false',
            'Listing Strategy': 'using chronological order',
            'List File Attributes': 'false',
            'Batch Size': '100'
        },
        state='STOPPED'
    )
)
pprint(canvas.list_all_processors(process_group_id=processor_loc))

# 运行processor
canvas.schedule_processor(processor)

# 获取文件
proc_state = None
while proc_state not in {'RUNNING', 'STOPPED'}:
    processor_data = nipyapi.canvas.get_processor(processor.id, 'id')
    proc_state = processor_data.status.aggregate_snapshot.status

# 获取文件列表
file_listing = nifi.get_all_flowfiles(
    nifi.list_all_processors(process_group_id=processor_loc)
    ['processors'][0]['