List of Authentication Tokens Wiped Out

I logged into one of the ~100 WordPress sites I host and found a warning that my authentication token was bad. I logged into wordpress.sucuri.net, and found the following error: “You don’t have any WordPress sites with the plugin being monitored. Please add one here.” So, somehow during the past week, my list of ~100 authentication tokens was wiped out. I would like to know how this happened, and what can be done to resolve it–preferably without having to re-enter all tokens by hand.

https://wordpress.org/plugins/sucuri-scanner/