Site accessibility & firewall considerations (Error 404 or Load Failed)

Created by Damien Zwillinger, Modified on Mon, 28 Aug 2023 at 11:53 PM by Damien Zwillinger

Applies to:

  • Velixo NX
  • Any ERP


Modern Excel add-ins cannot make a direct connection to your ERP system due to the browser engine restrictions for cross-origin requests.  In Excel for Mac and Excel Desktop for Windows, MS Office utilizes a Safari or Edge-based browser engine behind the scenes.


Therefore, Velixo NX uses a secure proxy server to facilitate the connection to your ERP system.   The proxy never caches or stores your ERP data, it is used solely for authentication and request pass-through. 


However, the fact that such a proxy server exists has two important implications:

  • Any ERP site that you connect to must be accessible over the public internet, with no VPN requirement

  • If your ERP host uses a firewall, it is important to allow-list not just your end users' IP addresses, but also those of Velixo NX's proxy servers


IP ranges and addresses for allow-listing:



If those IP ranges and addresses are not allowed, this can result in errors during the connection process, such as Error: "504" or Error: "Load Failed".

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