oVirt 4.4 requires engine and hosts based on RH EL / CentOS 8, while your current env in 4.3 has them based on RH EL 7 / CentOS 7. You have to reinstall the node that you isolated with the engine.

So after taing the engine at its latest 4.3.x level and rebooting the 4.3 engine OS, you have to follow the steps described in 6.5: stop the ovirt-engine service, take a backup and copy the generated file outside of the env, scratch the engine and related node and reinstall it with 4.4 ovirt node and then on the host, now in 4.4, run the command 

hosted-engine --deploy --restore-from-file=backup.bck

and so on...

Gianluca