Thanks for your reply! I have tried updating the key but that just appears to create a new key. I still get the same "gateway failed to pass the authentication" message when I try to send a task.
The key was set by a previous employee so we don't know the keystore password nor the expiration date. We reached out to him to see if he remembered the password but he did not have it.
Where is the database stored? I believe we were backing up our templates and images but that's it (well along with the original ks file). We use the Postgre database rather than SQL server.