A member of riot sent me this in a ticket and It worked for me, hope it helps!
Some players experience a bug in the patcher that results in the patch getting "stuck" at 33%. However, rest assured that the patch is still downloading. The easiest way to see its progress is to look in the upper right corner of the top progress bar. You should see the MB remaining displayed. If this number is changing then you are still patching properly. You simply need to leave the patcher open wait for the patch to complete.
You can try to fix this issue by disabling Peer-to-Peer via the following instructions:
- Open League of Legends Patcher.
- Select the gear-button in the top right-hand corner of the Patcher window (the first window that appears)
- Disable Peer-to-Peer Transfers.
- Save Settings.
- Restart PC