We have ~190 switches scanned by IP using SNMP credentials. Scan runs daily at 12 noon. This has been configured and stable for about a year. No other items are scanned by IP.
I checked the list for a report recently and found that the Last Seen date as stopped updating and the switches are marked as non-active now.
The scans continue to run daily, and I have verified by 1) watching the IP scanning queue at the scheduled time, and 2) changing the schedule time on certain switch IP addresses to current time and watching the queue populate & empty as expected, then returning them to the original time.
The data listed for the switches is correct and current! It does reflect expected daily changes. So, I'm comfortable that the scanning is good and accurate, just the last seen date isn't being updated in the database.