I have no idea how to resolve your specific issue.
This month, due to the launch of an On3 app, there was a change in logging in. Perhaps the change impacted you. If the below info doesn't resolve things, then contact the On3 Support at the below contact.
The info:
On3 is currently creating an app that
will require users to log in using their email address instead of their username, starting in May, on both the website and the app. If you're already logging in with your email, nothing will change for you. You can find the email address that you registered with at
https://www.on3.com/my/settings/.
Please note that although your username will continue to be displayed on the forums, it will no longer be used as a login credential.
If you wish to update your registered email address, contact On3's support team at
[email protected].