schedule not running; manual backups not sending to dropbox

Very recently my snapshot pro setup has simply not been working. Any scheduled backups do not run, the next file send is dated, destinations are listed as pending, and manually creating backups does not send the files to dropbox.

WP_CRON is enabled in my wp-config file, the memory limit is at 512M, and any errors are are sent to a log file. I've checked both the php log and the log for the last successful scheduled backup, but there's no errors found in either. I've also gone to /wp-cron.php on several sites to no avail.

I have WP Crontrol enabled, and the snapshots appear in the Cron Schedules but not the Cron events.