Me and other developers I know using git lfs have been having the issue that certain files are not getting downloaded completely when pulling/checking out the newest commit.
Some of our blueprint assets will end up with a size of 1kb. (i believe this may just be a pointer?)
FIX: Go to cmd line in Sourcetree and type “git lfs pull” to get the remaining files.
It will finish without getting to 100% of the repo, which is what you want. Refresh your project and open again, you should have your files.
Just happened to me on my TestingGrounds, as I do this tutorial from two different computers.