VMware vCenter Server 7.x
The appliance is missing localhost in /etc/hosts file, or the /etc/resolv.conf does not have proper DNS servers listed.
/etc/resolv.conf should have primary and secondary DNS servers per install, and this can be manually changed by editing this file post install if that does change and VAMI is not accessible.
/etc/hosts should originally look similar to:
# End /etc/hosts (network card version)
# VAMI_EDIT_BEGIN
# Generated by Studio VAMI service. Do not modify manually.
##.##.##.## <server name>.example.com <server name> <server name>
##.##.##.## <server name>.example.com <server name> <server name>
# VAMI_EDIT_END
# End /etc/hosts (network card version)
# VAMI_EDIT_BEGIN
# Generated by Studio VAMI service. Do not modify manually.
127.0.0.1 <server name>.example.com <server name> localhost
::1 <server name>.example.com <server name> localhost ipv6-localhost ipv6-loopback
# VAMI_EDIT_END
Skyline Health Diagnostics can be used to detect and provide remediation to issues in the vSphere and vSAN
https://knowledge.broadcom.com/external/article/345059/vmware-skyline-health-diagnostics-for-vs.html