@MichaelDol I think that's a different issue which was related to the version of OpenStudio provided in Revit being incompatible with certain chipsets and in that case the only error received just said that the report wasn't generated.
The error message that @z5371336 has is different and maybe implies that the OS application is not installed on the PC?
The user may have uninstalled the application.
I see to have open studio in the file path location, put it opens up for a second and then closes. do i need to install something?
Just realised I was still working on Revit 2021, thats why my directory was trying to open the Open Studio CLI for Revit 2021, but have installed revit 2023 and all working now. Thank you anyway for your help