Toad Error using Proxy Connection

I created a login for a user two days ago to an oracle database and altered another user so this new user could do a proxy connection as that user. Everything worked fine that day and the user was able to connect from Toad using username[proxy_as_user]. Today this same connection gives an error of ORA-6413: Connection not open.. The user can connect as themselves (not proxying) without issue from Toad. They can also connect from sqlplus using the proxy connection without issues, so we know the DB is fine and their oracle client is fine.

Toad Version: 10.6.1.3

Oracle Client: 11.2.0

Oracle Database: 11.2.0.4

I tried turning on sqlnet tracing, but it doesn't seem to log anything for these bad connections.