Hello
Your probably looking for something that sends a heartbeat from your log shipper. Perhaps something like this.
I have widget on a dashboard that show is the source count and if it goes up/down but I haven’t configured something to notify me when it does.
If you looking for report you may want to look into the Enterprise version of Graylog OR
this also could be possible through the Event definition /w Aggregation. You would need to adjust the time for 24 hours and make sure you have the correct fields for “errors” -n- “source”. This would depend on the INPUT , type of logs and what kind of log shipper you are using.