I usually use libreddit to read/browse/lurk, but occasionally I want to sign in to post or PM someone.
I wasn't able to login, and after a quick panic, I found discussion stating that reddit will sometimes prevent logins from the Tor network and provide a false, "Invalid Password" message to dissuade use. The account in question was created on Tor, and only accessed via Tor.
I disabled JS completely and tried again, as suggested, and by god it worked.
Additionally, a few weeks back I made a new reddit account via Tor that was going to be for a hobby specific use. I don't want my accounts, interests, and other things all under one account so it seemed like a good idea to just create a new account that I'd use only for that hobby specific discussion. Account was created fine, I create a new post on a small sub for the hobby in question and PM the mods to let them know I created a new account, not a bot, and it was just a regular post (They had a pinned topic stating to do this for new accounts). They respond back and tell me that they're getting a, "User not found" message. I logged out, went to my profile URL and sure as shit, less than 20 minutes after signing up, my account was shadowbanned. Logged in, zero indication of this.
Anyway, reddit and Tor is a volatile mix. Good luck.