2FA “one-time password URL is incorrect”

I set up 2FA on my account a couple of weeks ago. I even logged out and logged back in with it after the fact to make sure I got it working properly.

Yesterday, when I tried to log in again, I got the following error: “The one-time password URL is incorrect: check the URL and try again. If you still have trouble, contact support for the site.” I'm using 1Password.

I might have done something wrong. I could use some pointers on how to address it.