nutclient 1.5.1 failing authentication

[cbprp2576]

Describe the bug

nutclient fails authentication to NUT server.

Expected behavior

Successful authentication as credentials are correct.

Actual behavior

ACCESS DENIED: LOGIN rejected: ACCESS-DENIED
Access denied - credentials are wrong. Stopping monitor. Fix nutclient.json and restart.

Steps to reproduce

1. Confirmed credentials are valid (same credentials used in another client app work successfully)
2. stop service. start service. verify service running. view log.
3. try interactive (.exe).

Environment

• NutClient version: 1.5.1
• OS / distro: Windows Server 2019 & Windows 11 Pro 25H2 (26200.8457)
• NUT server type and version: Nutify 0.2.2.0-amd64 & 0.2.2.3-amd64
• UPS model: CyberPower LX1500GU3-FC
• Architecture: x86_64, arm64

nutclient.json

Please paste your config below, with passwords removed:

{
  "NutServer": {
    "Host": "10.1.1.215",
    "Port": 3493,
    "UpsName": "CBP-UPS-1500",
    "Username": "cbpupsobserver",
    "Password": "{LONG PWD REMOVED}"
  },
  "Monitoring": {
    "PollIntervalSeconds": 5,
    "ShutdownDelaySeconds": 30,
    "ShutdownCommand": "powershell.exe",
    "ShutdownArguments": "-ExecutionPolicy Bypass -File C:\\Scripts\\graceful-shutdown.ps1",
    "LogFile": "C:\\Scripts\\nutclient.log",
    "StatusFile": "C:\\Scripts\\nutclient-status.json",
    "BatteryChargePercent": 30,
    "BatteryRuntimeSeconds": 120,
    "InputVoltageMinWarn": 100,
    "LoadPercentWarn": 70,
    "DeadTimeSeconds": 30,
    "PreShutdownCommand": null,
    "PreShutdownArguments": null,
    "PreShutdownDelaySeconds": 5,
    "LogMaxBytes": 1048576,
    "LogLevel": "events"
  }
}

Log excerpt

Relevant lines from /var/log/nutclient.log (Linux) or C:\Scripts\nutclient.log (Windows):

2026-05-26 12:43:09 NUT UPS Monitor started
2026-05-26 12:43:09 Monitoring CBP-UPS-1500@10.1.1.215:3493
2026-05-26 12:43:09 Shutdown delay: 30s
2026-05-26 12:43:09 Shutdown command: powershell.exe -ExecutionPolicy Bypass -File C:\Scripts\graceful-shutdown.ps1
2026-05-26 12:43:09 ACCESS DENIED: LOGIN rejected: ACCESS-DENIED
2026-05-26 12:43:09 Access denied — credentials are wrong. Stopping monitor. Fix nutclient.json and restart.
2026-05-26 12:43:09 NUT UPS Monitor stopped

Status file

Contents of nutclient-status.json at the time of the issue:

{
  "server": "10.1.1.215:3493",
  "upsName": "CBP-UPS-1500",
  "state": "Error",
  "currentStatus": "OL",
  "batteryCharge": 100,
  "batteryRuntime": 5200,
  "inputVoltage": 120,
  "upsLoad": 11,
  "lastPoll": "2026-05-26 10:57:31",
  "consecutiveFailures": 24,
  "history": [
    {
      "time": "2026-05-26 11:19:11",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 11:18:09",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 11:17:08",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 11:16:07",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 11:15:06",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 11:14:05",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 11:13:04",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 11:12:03",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 11:11:02",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 11:10:01",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 11:09:00",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 11:07:59",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 11:06:58",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 11:05:57",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 11:04:56",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 11:03:55",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 11:02:54",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 11:01:53",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 11:00:52",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 10:59:51",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 10:58:50",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 10:58:08",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 10:57:47",
      "status": "error",
      "event": "Connection to 10.1.1.215:3493 failed: No connection could be made because the target machine actively refused it."
    },
    {
      "time": "2026-05-26 10:57:36",
      "status": "error",
      "event": "Connection closed by server"
    },
    {
      "time": "2026-05-26 10:57:31",
      "status": "OL",
      "event": "poll"
    }
  ]
}

Additional context

Other client app that is successful (but can't be used to shutdown servers. Windows user client only):
https://github.com/nutdotnet/WinNUT-Client/releases/tag/v2.3.9492

Thanks.
73