Versions are useful, as are screenshots - then possibly logs.
I have this same issue. I'm trying to rename my ESXi hosts from IPs to hostnames.
- Put ESXi host and datastore in maintenance mode
- vSphere: Remove from cluster (if necessary).
- ESXi host: Remove /etc/vmware/ssl/rui.* Run services.sh restart or reboot.
- Try to re-add host by hostname from vSphere -- works, detects certificate and when you press finish you see an "Add hosts" task report error:
- A general system error occurred: Unable to get CSR from host <hostname>
All hosts have the other hosts in /etc/hosts and can ping by hostname. NTP is in sync across ESXi and VCSA.