The isolation address is not configured for vSphere HA for the corresponding cluster.
/var/log/vmware/vcf/domainmanager/domainmanager.log
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YYYY-MM-DDT00:22:42.646+0000 ERROR [vcf_dm,0b4b0222496e4eb6,1e19] [c.v.v.c.c.f.a.i.BaseHaIsolationAddressOptionsAction,dm-exec-1] Not found advanced option for isolation address 192.168.8.1 YYYY-MM-DDT00:22:42.654+0000 ERROR [vcf_dm,0b4b0222496e4eb6,1e19] [c.v.e.s.o.model.error.ErrorFactory,dm-exec-1] [2QDKT4] VALIDATE_VSPHERE_HA_ISOLATION_ADDRESS_OPTIONS_CONFIGURATION_FAILED Validate Configure High Availability Isolation Address(es) failed for Cluster domain-c8 com.vmware.evo.sddc.orchestrator.exceptions.OrchTaskException: Validate Configure High Availability Isolation Address(es) failed for Cluster domain-c8 at com.vmware.vcf.common.contract.fsm.actions.impl.BaseHaIsolationAddressOptionsAction.postValidate(BaseHaIsolationAddressOptionsAction.java:158) at com.vmware.vcf.common.contract.fsm.actions.impl.UnConfigureHaIsolationAddressOptionsAction.postValidate(UnConfigureHaIsolationAddressOptionsAction.java:131)
1. Login to the vSphere UI for the vCenter(s) in question.
2. Select the affected cluster at which the removal of the host is failing
3. Select Configure > Under Services, vSphere Availability > Edit
4. Select Advanced Options
Option1: Configure a vSphere HA Isolation address.
Add a line or enter the key in the option field and its corresponding value as shared below and click OK.
Option2: Remove vSphere HA Isolation address.
5. Disable and re-enable vSphere HA on the cluster for the changes to take effective.
6.Re-try the task of host removal from SDDC.
For more information on vSphere HA options please refer to:
https://docs.vmware.com/en/VMware-vSphere/7.0/com.vmware.vsphere.avail.doc/GUID-E0161CB5-BD3F-425F-A7E0-BF83B005FECA.html