In 2019, repository access was changed to use API tokens instead.
You can create them for your account here: https://www.curseforge.com/account/api-tokens
You should then do a fresh checkout of your repository since the URL has changed a bit.
After that, committing should work again using your username and the API token created before as password.
Be warned that they are currently having some problems with the packager not automatically starting for all projects so you might have to manually trigger that. 🙈