I had the same message today, after searching for a solution , I found something :
I use a cron job on the server , not these from wordpress .
Wordpress timer for this job is set to 3600 sec (hourly) , but the cronjob on server was set to more than one hour ((once a day).
Changing this to one hour solved the problem (in my case).
So CRON JOB must run at least ONCE an hour to be ok.
I think check plugin settings if you use plugin , or adapt crontab on the server
