What did the message tell you? Your email suddenly started sending the server No Such User messages.
A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed:
host gmail-smtp-in.l.google.com [**.***.***.26]
SMTP error from remote mail server after RCPT TO:<**********@gmail.com>:
550-5.1.1 The email account that you tried to reach does not exist. Please try
550-5.1.1 double-checking the recipient's email address for typos or
550-5.1.1 unnecessary spaces. Learn more at
550 5.1.1
https://support.google.com/mail/?p=NoSuchUser u21si10907561jap.24 - gsmtp
When the server gets a bad email warning, it locks your account and notifies the admin.
You sent an email at 2pm asking for help. The tech replied at 5pm. Should be working now.