Error Codes

Every error has a code, description, and specific fix. These appear in toast notifications and in the Management panel's Error Logs.

Authentication Errors

AUTH_429 — Auth Rate Limited

Roblox rate limited the auth ticket request. Too many accounts launched too quickly.

Fix: Increase wave delay to 15-20s in Settings → Launch. Wait 2-3 minutes before retrying.

AUTH_FAIL — Auth Ticket Failed

Could not get an auth ticket. Cookie may be expired, IP-locked, or rejected.

Fix: Run Health Check to verify the cookie. If expired, remove and add a fresh one from the same PC/network.

CSRF_FAIL — CSRF Token Failed

Could not get a CSRF token. Usually a temporary Roblox server issue.

Fix: Wait 30 seconds and retry. Check status.roblox.com for outages.

Cookie Errors

COOKIE_EXPIRED — Cookie Expired

The .ROBLOSECURITY cookie is dead. Roblox invalidated it after a password change, security sweep, or IP change.

Fix: Remove the account and add a fresh cookie. Log in via incognito, copy cookie, close without logging out.

COOKIE_IP — Cookie IP Mismatch

Cookie was last used from a different IP. Roblox ties cookies to their authentication IP.

Fix: Get cookies on the same PC and network where Alt Central runs. Don't use cookies from proxies.

Roblox Errors

ROBLOX_529 — Roblox Server Error

HTTP 529 — Roblox servers are overloaded or under maintenance.

Fix: Wait a few minutes. Check status.roblox.com.

ROBLOX_NOT_FOUND — Roblox Not Installed

RobloxPlayerBeta.exe not found in the expected location.

Fix: On VPS, create a junction link:

mklink /J "%LOCALAPPDATA%\Roblox\Versions" "C:\Program Files (x86)\Roblox\Versions"

Otherwise, reinstall Roblox from roblox.com.

Multi-Instance Errors

MUTEX_FAIL — Mutex Failed

Could not acquire the singleton mutex for multi-instance.

Fix: Close all Roblox windows, wait 10 seconds, retry. If using Fishstrap/Bloxstrap, enable "Allow multi-instance launching" in their settings.

MULTI_INSTANCE_FAIL — Multi-Instance Failed

A Roblox instance was killed when another tried to launch. The bootstrapper is blocking multi-instance.

Fix: Open Fishstrap/Bloxstrap settings → enable multi-instance → disable confirm launches → restart bootstrapper.

License Errors

HWID_MISMATCH — HWID Mismatch

Hardware ID doesn't match the license. Each license is locked to one device.

Fix: Contact staff for HWID reset via Management → User Lookup.

LICENSE_EXPIRED — License Expired

License key has passed its expiry date.

Fix: Purchase a renewal at the website.

PRC Errors

PRC_401 — PRC API Unauthorized

Invalid or expired PRC API key.

Fix: Regenerate the API key in ERLC private server settings → ER:LC API → paste in Settings.

PRC_422 — PRC Command Rejected

PRC rejected the command format.

Fix: Commands must start with : (e.g., :h Hello). Check PRC docs for valid syntax.

Launch Errors

LAUNCH_FAIL — Launch Process Failed

Could not spawn RobloxPlayerBeta.exe. Antivirus, permissions, or bootstrapper interference.

Fix: Add Alt Central to Defender exclusions. Enable multi-instance in bootstrapper. Try running as administrator.

REJOIN_FAIL — Auto-Rejoin Failed

Account dropped and rejoin failed. Cookie may have expired mid-session.

Fix: Run Health Check. If cookie is valid, increase watcher interval. If expired, replace it.

DEFENDER_BLOCKED — Windows Defender Blocked

Windows Defender quarantined backend.exe.

Fix: Windows Security → Protection history → find backend.exe → Allow. Or add the Alt Central folder to exclusions.