I'm deploying a new HX cluster and hitting this error on all of my nodes. (IPs change per node respectively)
ESXi reachability check
IP address: 172.20.7.22 at default port: 902 is not reachable.
This is all internal and not going out through a firewall.
These connectivity issues from the installer are usually related to the installer guestVM port-group/vlan settings. If you can reach the installer guestVM connections just fine from your desktop, then perhaps your upstream switch (above the FIs) does not have the vlans correctly configured, and the L2 traffic bound for the esxi mgmt interfaces is not making it.
I would check for the mac address of the esxi hosts in question in the FI mac address tables, and confirm they are being learned in right vlan. If they are, and aren't aging out, then the issue is likely the upstream switches.