No errors were logged in system log and Application module diagnostic event log. But the windows application event log (Start Menu -> Event Viewer -> Windows Logs -> Applications) captured "Error Caught in Application_Error eventError in: https://*ServerName*/ion/Historical/DisplayLogs.aspx?queryId=0a92b9b3-4797-4e92-8da1-4d43988b8615&dgm=x-pml:%2fdiagrams%2fud%2fdefault%2f8000_FAC-PQ-61850-4WYE_V1.0.1%2f8000_FAC-PQ-61850-4WYE_V1.0.1-logs.dgm&node=ST_IVE.PM8240&logServerName=QUERYSERVER.ATAL&logServerHandle=327952&isEventLog=Error Message:Could not find file 'C:\Program Files (x86)\Schneider Electric\Power Monitoring Expert\system\etc\IonNames.en-US.resx'."
It can be another IonName.[Language].resx file as well.

Cause
This was probably an upgraded system where the diagram link was referencing an existing resx file that in the current version has been renamed or does not exist anymore.

Resolution
Navigate to C:\Program Files (x86)\Schneider Electric\Power Monitoring Expert\system\etc
Search for IONNames.[LANGUAGE_DESIRED].resx
Make a copy of it
Always keep the original in the folder
Rename the copy to match the file name that the error is claiming that could not be found
IIS reset and refresh the Web Page

Issue 2
Error opening a Datalog Viewer

Error Caught in Application_Error event
Error in: https://wasg00115/ion/Historical/DisplayLogs.aspx?queryId=8a2a27f8-a578-43bf-9b3c-cb49a19cdef6&dgm=x-pml:%2fdiagrams%2fud%2fdefault%2fPM820_FAC-4WYE_V1.1.5%2fPM820_FAC-4WYE_V1.1.5-rev.dgm&node=HUB-L4.PM-MSB-INC&logServerName=QUERYSERVER.TNETVMPME9&logServerHandle=327952&isEventLog=
Error Message: An error occurred in GetConnectionStringFromQueryServer calling method lsSetupObject.GetConnectionString while attempting to access Query Server [QUERYSERVER.OLD_SERVER_NAME] with handle [327952].<br>With moniker: pmlitem:QUERYSERVER.TNETVMPME9:pmlnew:PMLQueryServer.IONModuleInfo:<br><br>The Query Server may not be running.<br>
Stack Trace:   at WebReach.Historical.MapPegQueryToSQL.GetConnectionStringFromQueryServer(String lsSoftwareNode, String lsHandle)
at WebReach.Historical.MapPegQueryToSQL.Execute(Int32 numRecordsToGet, String dgm, String node, String queryId, String isEventLog, String logServerName, String logServerHandle, String whereClause)
at WebReach.Historical.MapPegQueryToSQL.Execute(Int32 numRecordsToGet, NameValueCollection args)
at WebReach.Historical.DisplayLogs.Page_Load(Object sender, EventArgs e)
at System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e)
at System.Web.UI.Control.OnLoad(EventArgs e)
at System.Web.UI.Control.LoadRecursive()
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

Cause
This issue happens when the device icons are pasted in custom diagrams and query server is not properly set in the custom vista diagram pages. When check the url when a meter template is opened you can see the query server name weater it is properly passe or not -
https://wasg00115/ion/default.aspx?dgm=x-pml%3a%2fdiagrams%2fud%2fdefault%2fPM820_FAC-4WYE_V1.1.5%2fPM820_FAC-4WYE_V1.1.5-rev.dgm&node=HUB-L4.PM-MSB-INC&logServerName=QUERYSERVER.OLD_SERVER_NAME&logServerHandle=327952
in this case the URL is pointing to wrong query server.

Resolution
Open the diagram in Vista and right click on page > Properties > Query server > Select 'custom query server' > click on "Edit Link" button > and select the local PME query server.
Restat  'ION Application Modules Core Services Host' service and refresh the browser