Download Cache contains broken files – There’s also a fairly common glitch that might occur in situations where there are a lot of pending items inside the Download queue.In this case, you can resolve the issue by deleting the corrupted mods and do an integrity scan. If this is a widespread issue, Steam will eventually refuse to download any new mods. !Workshop folder contains corrupted files – It’s also possible that this issue occurs because some of the mod files that you downloaded have become corrupted.
If this scenario is applicable, you can verify if the mods are actually downloading by switching to Big Picture Mode.