Unable to manage SolusVM VPS through WHMCS admin area: Unauthorized

Applicable to:

Unable to manage SolusVM VPS through WHMCS admin area:

SVM_ERROR: Unauthorized

Missing Custom Fields for the affected product in WHMCS.

Access WHMCS administrator area.
Open Setup > Products/Services > Products/Services > Edit for the affected Product.

How to edit a product
Open Custom Fields and add missing fieles according to virtualization.

Example of custom fields for OpenVZ
Open Clients > Products/Services > affected Product.
Add vserverid and nodeid in relevant fields.

vserverid can be found in SolusVM > Virtual Servers > ID column.
nodeif can be found in SolusVM > Nodes > ID column.

Example of correct fields.