When you attempt to authenticate using known valid credentials, authentication fails. Attempts to authenticate generate an entry in the event log. "Licensing service is not running."
Either the Customer Portal subscription is not set up properly or the AuthAnvil subscription details are incorrect. Each time the service starts it attempts to connect to the Customer Portal and log into your subscription using the configured email account and password. If the login fails, the service will stop, so as to prevent authentication attempts until this issue is addressed.
Log into the Customer Portal and navigate to Account > Manage Subscription > Manage Subscription Settings.
Ensure the account is active and set the password to to the value you want to use during the AuthAnvil configuration.
Next, open the AuthAnvil Configuration Wizard and, on the Subscription Details dialog, confirm that the email account and password are correct, then complete the Wizard. If the service starts successfully it will attempt to send a licensing report the Customer Portal.
If its successful then you should now be able to authenticate again.
Note for MSPs: If you had to change the password, you will will need to confirm this information on each of your clients' AuthAnvil servers. Check each event log for the successful sending of the licensing report.
AuthAnvil 2FA v4 and older.