This is the module configuration issue. This is happening when there is not any host is enabled/activated with a specific data center.
To fix this error, follow the given below steps.
1. Go to "WGS VMware" addon module >> "Provisioning Setting" with WHMCS admin. Click on specific Datacenter and then make sure this option "Disable ESXi/Host" should not be enabled. If enabled then untick this option and save the changes.
2. Go to "System Settings" >> "Products/Services". Edit that specific product and then click on the "Module Settings" tab. Here is the select box with the name "Select Host". Select "None" or make sure the selected host must be in that ordered Datacenter and not be disabled from "Provisioning Setting" under "WGS VMware" addon module.
To find the "Datacenter", just edit the purchased client product/service and find the "Datacenter".
