Upload Tool: Randomly Stopped Working

I have had an automated version of the upload tool working for about a year and a half now. Yet I noticed it stopped randomly last month. The only error that I get now is this:

ServerException (HttpStatusCode 200 Error Code: 407 , URI: https://accounts.zoho.com, Action: ZOHO_LOGIN, Message: Could not login. Could be because of username/password mismatch)

Any ideas? I changed nothing. I went back and looked at the username and passwords and they are all fine. Any ideas?