Agent controller not registered

CMK Version: 2.1.0 RAW
OS: Windows Server 2019
Agent controller not registered

After multiple clean installations specifically on this server I can’t get CheckMK to work.
The service is started.
With telnet i can connect to the agent from the OMD server.
I get a return with value: 16
The web test connection has a successfull ping but the agent output is: Agent controller not registered
I’ve successfully registered the controller but sadly this didn’t change anything. I currently have Checkmk running on about 50 windows devices and haven’t seen this issue yet.

Any help would be appreciated.

Double-check your registration process. Most likely you mistyped the hostname.
Additionally check out this troubleshooting section.

Hi Robin,

Thanks for replying! I was indeed being a bit stupid.
I’ve only recently started working at this company, i thought there were 3 vm’s File, File01 and File02.
Apperantly the “File” server was a dns name which opens up the “master” machine as the File01 and File02 are setup in HA.

Glad to here you could fix it!
If those names are your actual host names, maybe the first order of business for you should be to start a proper naming concept, as a poor naming concept can cause you quite some pain.


same failure here. In 2.1.0p4, host cannot registered. Hostname is correct. Query status successfull.
But host didnt register to CMK. In our environment are two Windows Server 2016. There’s no firewall between, test ok, telnet “16”. Multiple times re-install. No chance to register these servers.


Is the host TLS registered?
“C:\Program Files (x86)\checkmk\service\cmk-agent-ctl.exe”" register --hostname %host% --server [Put CHECKMK server here] --site [Site name here] --user automation --password [Put password here]"

Yes. Host has already been removed, added back for registration. Everything that is in the manual. No success.

What is the output of cmk --debug -vv [hostname] from the omd cli?

Check_MK Agent Version: 2.1.0p4, OS: windows, Update error: The agent updater is not registered at the deployment server(!), No successful connect to server yet(!), Agent plugins: 6, Local checks: 19

cmk “status” on host: Version 2.1.0.p4
Agent socket: operational
Connection: “cmk server”
UUID: bf2dexxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
Connection type: pull-agent
Certificate validity: Tue, 05 Jul 2022

and so on.

I can see all services. everything is fine. Only the host wont register @ cmk server…
After 60 minutes, registration isn’t successfull.


registration process “old style”:
check_mk_agent.exe updater register
after this “new” registration process, Service restart.

Registration successful,

1 Like