We recently bought a second ESM to create an HA cluster. Clustering and syncing went fine, but our redundant ESM can't communicatie with the ELM.
In the GUI there's a question mark on front of the ELM device, when I click the question mark, I get the error "The status of the device couldn't be retrieved due to not being able to connect to the device.". When I try to set up an SSH session from the redundant ESM to the ELM, I get the message "No RSA host key is known for 192.168.xxx.xxx and you have requested strict checking. Host key verification failed.".
I tried rekeying the ELM from the primary ESM, but this didn't help either. There are no firewalls to blame; communication between the devices has been allowed.
Try disable strict host check on the ELM:
ssh -o "stricthostkeychecking no" root@<IP address of the ELM>