Ref: Blueprint.pak I have a route (Springfield) that no longer works, no idea what happened and support won't allow me to repurchase it so I'm seeking help. See Ref: does this file suppose to have information in it because it does not. Is this then considered a corrupt file?
Once you have purchased something thru Steam there is no need to buy it again. Even if you did it would be no different to the version you have now as the files would be the same. You have already opened one thread - why are you opening another? https://forums.dovetailgames.com/threads/springfield-line-springfield-–-new-haven-route.95201/ I suggested you do a File Verification - have you done that?
You can uninstall it, then install it again. On your Steam home page, go to Library, click on that, then right-click on Train Simulator Classic, then select properties in the menu that comes up, click on DLC. This will show all your TSC DLC. In the search box, type Springfield Line when it comes up, untick the box to uninstall it wait about 40 seconds, then tick the box to install it again. I have The Springfield Line and it works perfectly for me.