For anyone else encountering this issue:
For the past two years, VCS clients were supposed to be using an API key instead of CurseForge credentials since CurseForge was switched over to using Twitch accounts and its own authentication system was decommissioned.
Early in April, every bit of the old authentication code was removed from the sites which brought to light the fact that in some cases the old credentials had been erroneously accepted. To fix this, go to the site your projects reside on and click your name on the top navigation bar. On the dropdown, select "My Account" and on the next page click into the My API Tokens tab. From there you'll be able to generate a new API token which you would use as the password in your VCS client.