After vCenter Server Major upgrade ESXi fail to reconnect to VCSA and/or show error "Cannot upload agent"

Products

• VMware vCenter Server 7.0
• VMware vCenter Server 8.0

Issue/Introduction

Static Routes are configured in the environment.

Version upgrade has successfully completed on vCenter.

After upgrade, ESXi hosts fail to reconnect to vCenter Server and/or the message "Cannot upload agent" is seen in the VCSA UI for all ESXi hosts.

Environment

vCenter Server 7.0 

vCenter Server 8.0 

Cause

Static routes configured in the environment are flushed after a major upgrade.

Resolution

Reconfigure the Static Routes after major upgrade; see Configuring Persistent Static Routes on VCSA for steps on this. 

All hosts should then show as connected after those steps are followed.