SDLXLIFF Convertor for MS Office for Studio 2021

Hi,
We have problem with SDLXLIFF Convertor for MS Office for Studio 2021. We have the version for 2021, but trying to convert we every time receive error message in the Windows system language (Czech) - translated to English it is like "Unable to load file or assembly DocumentFormat.OpenXml, Version 2.9.1.0, ...". Can anybody advise or help please?

Thank you.