I downloaded a torrent file and it was re-checking the files which I already had in my incomplete path. When it gets to 100% it should move everything to the Save path and start Seeding.
Instead, it, silently, encountered an error moving some of the folders/files (Path too long) and therefore could not/would not seed even though I had all the files.
I was able to solve it by shortening the path but it would have been nice it QB had told me about this error somehow so I knew what was happening.