It is a bug in some of REX installers that they are blaming on Window 11 / OneDrive. Started after a Windows System Update back in October and the REX guys refuse to fix it. They keep blaming OneDrive and have proposed a silly workaround using a symbolic link. There is another thread mentioning this here and on Discord.
I tried to work it through with them a couple of months ago but lost my patience and gave up. They are knowingly selling a product they know has compatibility issues with the current version of Windows. Shame on them.