Hello,

We are facing a critical issue with CODESYS
SoftRedundancy that we have been unable to resolve despite
extensive troubleshooting.

HARDWARE:
2× HP EliteDesk 800 G9 SFF
Intel Core i7-14700 (20 cores)
16GB RAM, 512GB NVMe SSD
Windows 11 IoT Enterprise LTSC 2024
NIC1: Built-in Intel GbE
NIC2: Intel I210-T1 PCIe (NIC team)

SOFTWARE:
CODESYS Control Win V3 - x64 Version 3.5.22.10
CODESYS SoftRedundancy SL
Server 1 IP: 172.10.10.101 (PLC1 — Active)
Server 2 IP: 172.10.10.102 (PLC2 — Standby)

CURRENT CODESYSControl.cfg:
[CmpRedundancy]
BootupWaitTime=120000
StandbyWaitTime=12100
SynchronousTimeout=12100

[CmpSchedule]
ProcessorLoad.Maximum=80
WatchdogTime=12000
WatchdogTimeoutAction=0

CONFIRMED WORKING:
PLC1/PLC2 identification configured via IDE
Connection IP configured via IDE
AutoSync enabled and written via IDE
Normal Active/Standby operation working
Server 2 auto-promotes when Server 1 completely fails

PROBLEM DESCRIPTION:
When NIC1 cable is removed from Server 1 — both servers
go to standalone mode.

When NIC1 cable is reconnected — both servers remain in
standalone indefinitely. Neither server auto-recovers to
Active/Standby without manual CODESYS service restart.

AutoSync fires (!!! Autosync !!! visible in log) but
recovery does not complete.

Tested with direct cable (no NIC team) — same result.
Confirmed not a hardware or NIC teaming issue.

KEY LOG MESSAGES:
"Timeout: No sync message RMSG_StartCycle (5)
from master: Standalone"
"Socket on other side closed gracefully 0"
"Standby PLC: Open acyclic work socket failed"
"Connection broke after 11806ms. Check BootupWaitTime."
Autosync(fires but does not complete recovery)

PCAP ANALYSIS (Wireshark):
CODESYS sync stops completely at T+3s
Server 1 sends TCP FIN on ports 1206 and 1208 at T+5s
No CODESYS redundancy traffic for remaining 24 seconds
Both servers stay standalone indefinitely

WHAT WE HAVE TRIED:

StandbyWaitTime = 12100ms
SynchronousTimeout = 12100ms
WatchdogTime = 12000ms (less than StandbyWaitTime)
AutoSync enabled
NIC2 set as Standby adapter
Disabled Windows Network Discovery
Direct cable test — rules out NIC hardware

QUESTION:
Per official CODESYS documentation: "No automatic
Reconnect is included in the functional scope of the
redundancy components. You can program the triggering
of a reconnect."

Is RDCY.Synchronize() the correct function to add to
our application for automatic recovery after both PLCs
go standalone?

What is preventing auto-recovery when AutoSync is
enabled and PlcIdent is correctly set?

Thank you for your support.