Observer log says, "Failed to read ArcGIS Server usage report "

[Royce_Simpson]

I'm having an issue with one of several monitored (2024.1.1) ArcGIS Server sites, where one of the sites is returning infrastructure metrics but no longer returning ArcGIS Server metrics.  When I go to the Observers page for that site, the "Metrics - ArcGIS Server" observer is showing "no data" and the log returns "Failed to read ArcGIS Server usage report". 

This site was working properly up until I patched (OS and ArcGIS Server) on the two ArcGIS Server VM machines and the associated web adapter VM machine last night. 

The other ArcGIS Server sites are being monitored properly after the patching, just this one is misbehaving.

Any tips on how to troubleshoot this?

[Royce_Simpson · Accepted solution]

We have a solution!  Per the advice from another thread here, I deleted like 20,000 old statistics files (\\myarcgisserversite\directories\arcgissystem\statistics).  Unregistered the ArcGIS Server component for the affected site in Monitor.  Deleted the usage reports for the site (https://myarcgisserversite.mydomain.org/arcgis/admin/usagereports).  Reregistered the ArcGIS Server site and bam, all the metrics fired back up.