During the Step 1 phase of an offline license activation, you may encounter a Red "X" error when attempting to upload the activation file the Citrix Cloud LAS portal.

This issue is typically caused by an upstream Proxy server or Layer 7 Firewall blocking the upload.
Note: The Citrix Cloud portal interface often masks the actual error response from your network security appliance. So, a generic red "X" is displayed.
Please check your proxy setting, and whitelist `las.cloud.com`.
This article describes a typical issue in LAS activation