Update
On April 1, 2020 Microsoft released the M365 E3 Unattended SKU and the Power Automate unattended RPA Add-on SKU. Please see review the two below references for more information.
Please click her to read the April 1, 2020 New Release
Please click here to download the Microsoft 365 Unattended License Overview (Nov 2020)
Please note even with the release of these new SKUs, Microsoft Office is not designed or supported to run unattended on a Windows Server as a server-side service.
For Excel server-side services, we recommend EPPlus - Please click here to learn about EPPlus
Original Post
Robotic Process Automation (RPA) is growing rapidly along with a large number of RPA tool vendors. Many of these tools automate reading and creating Microsoft Office files such as Excel workbooks and Word documents. We have heard some of these vendors require customers to install Microsoft Office on Windows Servers for the RPA agents to execute as a server-side service.
It is critical RPA tool customers understand Microsoft Office was not designed and is not supported to run unattended on a Windows Server as a server-side service. In addition to the technical and support issue of running as a server-side service on a Windows Server, there is the problem of licensing the software.
Please click here to read a Microsoft article covering this topic.