Zabbix Agent 7.4.3 and 7.4.5 not starting on Windows

[Robert W]

I have many servers (105) where these new agents wont start. I upgrade and start the service, the zabbix log only adds the below info, and after a while the zabbix agent stops.
So I have to downgrade on these servrers.
The servers are from different customers and different OS versions.

4748:20251106:082827.023 using configuration file: C:\Program Files\Zabbix Agent\zabbix_agentd.conf
9488:20251106:082902.499 Starting Zabbix Agent [VMDRIFT05]. Zabbix 7.4.5 (revision c525822dce0).
9488:20251106:082902.500 **** Enabled features ****
9488:20251106:082902.501 IPv6 support: YES
9488:20251106:082902.501 TLS support: YES
9488:20251106:082902.501 **************************

[BP_Vital]

Try to increase DebugLevel in zabbix_agentd.conf for more details.

[Robert W]

I have. And it still doesn't spit out anything more information :/

[Andrejs Poddubņaks]

Hi, Robert!
It seems that you are not facing a configuration error, but a bug in the Windows version of Zabbix Agent 7.4.x.
There is currently an open ticket in the Zabbix bug tracker — ZBX-27074: [ZBX-27074] Zabbix Agent 7.4.3 crashes during PDH initialization on Windows Server 2022 - heap corruption in zbx_get_all_counter_names() - ZABBIX SUPPORT
The symptoms are very similar to yours:
Agent 7.4.3/7.4.5 on Windows starts up, but the log only shows the block with “Starting Zabbix Agent / Enabled features,” after which, after a while, the process simply terminates without a clear error message. Exactly the same messages can be found in the official forum thread “Zabbix Agent 7.4.3 and 7.4.5 not starting on Windows”.
What you can do now:
1. The safest solution right now is to stay on the agent version that worked stably for you before the update (for example, earlier 7.4.x or 7.2/7.0) until Zabbix releases a fix for this bug.

2. Testing on a test host:
Enable detailed logging in zabbix_agentd.conf:

LogType=file
LogFile=C:\zabbix_agentd.log
LogFileSize=0
DebugLevel=4
​

3. Temporarily remove/comment out:
PerfCounter= / PerfCounterEn=
all Include files with custom .conf files that contain perf counters or complex UserParameters.
Try running the agent with the “minimal” configuration (without TLS, without additional modules).

4. Monitoring and waiting for confirmation
Keep an eye on ticket status ZBX-27074 in the Zabbix bug tracker and release notes for upcoming versions 7.4.x.

[Robert W]

Thanks!

Unfortunately 7.4.2 is not available on zabbix.com any longer :/