There is limited data on the error codes surrounding the SIEM, however, I am curious as to the image re-installed onto the receiver. Was it re-imaged to 9.4.x, or to an earlier version? Can the ESM SSH to the receiver?
I want to verify there is two way communication from the ESM to the receiver, and from the receiver to the ESM over port 22 to eliminate possible host fingerprinting issues, ssh key issues, or anything else between the devices.
To validate the build on the receiver, please either console (keyboard and mouse) to the receiver, or if SSH connectivity can be established, ssh to the receiver, and do the command "cat /etc/buildstamp" this will return the receiver build. If it is not the same version, you will need to get it upgraded to ensure connectivity between receiver and ESM can communicate properly.