@nathan_rudman - thanks for your suggestion. We offer both options at the moment so both are expected to work. If one of them does not work, then this needs to be shared with Anaplan Support for investigation.
Magali Pelissier, Product Manager - Extensions (Excel Add-in, PowerPoint Add-in, Google Sheets Add-on) Check out our dedicated Community page in the Platform section!
I got the support from Anaplan recently and the issue was resolved.
It was due to an old version of Microsoft NET Framework Set Up. So may be you want to try downloading the latest version (Microsoft. NET Framework 4.8), and install it before installing Anaplan Excel Add-In.
Remember to remove the current installed Anaplan Add-in before you update Net Framework.