Starting in release 5.2.0 of the SASE Orchestrator, the Classic UI will no longer be available to customers by default.
Classic UI can be enabled at customer level by going to Global Settings ----> Customer Configuration ---> Additional Configuration ---> Enable Classic Orchestrator UI
In some case,enable classic UI for entire VCO then you need to create VCO system property session.options.enableClassicOrchestrator and assign it's value as true
Classic UI Deprecated on the SASE Orchestrator
In Release 5.2.0 the New UI is now complete for all configuration and monitoring tasks. As a result, the Classic UI is by default hidden and not available for use. In addition, SASE Engineering will no longer fix issues that are specific to the Classic UI.
https://docs.vmware.com/en/VMware-SASE/5.2.0/rn/vmware-sase-520-release-notes/index.html