Customer receives the error: "Failed to upload activation request file. Please try again" after a few seconds when attempting to upload their Offline activation request file to Citrix Cloud

Developer tools analysis showed a 403 Forbidden error was being received from api-eu.cloud.com for the name: ImportOfflineActivationRequest at the same time as the error.
The customer had added https://api-eu.cloud.com to the list of allowed sites policy in their their firewall.
Although the customer connections to https://api-eu.cloud.com were allowed by their firewall, the customer's firewall logs showed that uploading files to https://api-eu.cloud.com were being blocked by another policy.
Creating an exception through the firewall to allow uploads to https://api-eu.cloud.com resolved the issue.
Customer receives the error: "Failed to upload activation request file. Please try again" after a few seconds when attempting to upload their Offline activation request file to Citrix Cloud
List of endpoints to be for LAS: https://docs.citrix.com/en-us/licensing/current-release/license-activation-service.html#citrix-cloud-commercial-endpoints