Some Package Servers are out of sync with certain packages, most likely new packages. Most Package Servers get the updates but there are some that don't.
Query to show Packages that have a Not Ready Status:
SELECT
vi.[Name] AS 'Package Server'
,pack.[Name] AS 'Package Name'
,fs.Name as [Orgination Server]
,osns.Id
,ps.[Status] AS 'Status'
,pack.[Package Version] as [Package Version on NS]
,ps.Version as [Version Last Reported by PS]
,ps.[PackageId] AS 'Package Guid'
FROM SWDPackageServer ps
JOIN ItemNSSource ns on ns.ItemGuid = ps.PackageId
JOIN OriginNSSourceNS osns on osns.Id = ns.OriginNSSourceNSId
JOIN ForwardServer fs on fs.Guid = osns.OriginNSGuid
JOIN vItem vi
ON vi.[guid] = ps.[PkgSvrId]
JOIN SWDPackage pack
ON pack.[PackageId] = ps.[PackageId]
AND pack.[_Latest] = 1
WHERE ps.[Status] != 'Ready'
ORDER BY vi.[Name], ps.[Status]
Status of Package is Not Ready
8.x
The solution we found was to restart the agent. Maybe the server hadn't been rebooted in awhile, but restarting the agent helped the agent to update package snapshots, etc. and resolve this issue.