As per R&D update, this can be a compatibility issue with the Windows and Office versions. The best way to troubleshoot this is by getting support from Microsoft. Raise a question for Microsoft support with the OS and Office version details to get their confirmation about the compatibility.

Windows Server 19 should support Excel web add-ins according to Microsoft-supported documentation.
https://learn.microsoft.com/en-us/office/dev/add-ins/concepts/browsers-used-by-office-web-add-ins#windows.

We are not able to proceed with MS about this issue. Can IFS provide assistance, to sort this combability error out, as the issue concerns multiple of customers. We have tried to solve this issue for the last 4 months. We have the same error message as mentioned above.

I can add to jolnse’s comment,

Upgraded to 23.2.3, downloaded a new xml add-in file, uninstall old Excel add-in, uninstall IE 11, enabled IE compability mode on edge and add the site to Internet Explorer mode pages, even tried to change default browser to Chrome, always with a restart of Excel in between.

Still got: User action cannot be completed because the browser version is not supported. Please check the IFS technical documentation.

Any more advice?

Hi @jolnse @EvrLeiflW ,

Please create a support ticket if you haven't already, or update existing cases with your feedback so that we can work to resolve this issue. If the issue concerns multiple of customers please update that as well. 

Thank you @Sachitha,

We have one in CS0177755.