Welcome, we arent the biggest club in the land of PSO2 bugs, but we do exist!
Im sad to say that there doesnt seem to be an easy answer for this one. I've tried all the google "fixes" and even done some command line digging to no avail. It feels like there is something inherently wrong with our microsoft windows 10 images or the server that pushes the download for PSO2 is shot. I'm very confused myself because I can download other apps fine but this one in particular won't work. Sadly these forums haven't helped one bit either and Im sorry I can't really give you more than what google would.