You cannot call a method on a null-valued expression.
At C:\Users\dhadmin\Desktop\generateReport.ps1:299 char:29
+ $ExchangeServer.Name.ToUpper <<<< ()
    + CategoryInfo          : InvalidOperation: (ToUpper:String) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

Attempted to divide by zero.
At C:\Users\dhadmin\Desktop\generateReport.ps1:299 char:171
+         Write-Progress -id 2 -activity "Exchange Server Information" -status "Determing Exchange information for: $($
ExchangeServer.Name.ToUpper())" -percentComplete ($p/ <<<< $ExchangeServers.Count*100);
    + CategoryInfo          : NotSpecified: (:) [], RuntimeException
    + FullyQualifiedErrorId : RuntimeException

You cannot call a method on a null-valued expression.
At C:\Users\dhadmin\Desktop\generateReport.ps1:303 char:57
+         $tServer.Add("Name",$ExchangeServer.Name.ToUpper <<<< ());
    + CategoryInfo          : InvalidOperation: (ToUpper:String) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

You cannot call a method on a null-valued expression.
At C:\Users\dhadmin\Desktop\generateReport.ps1:304 char:61
+         $tServer.Add("RealName",$ExchangeServer.Name.ToUpper <<<< ());
    + CategoryInfo          : InvalidOperation: (ToUpper:String) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

Get-WmiObject : Cannot validate argument on parameter 'ComputerName'. The argument is null or empty. Supply an argument
 that is not null or empty and then try the command again.
At C:\Users\dhadmin\Desktop\generateReport.ps1:310 char:66
+         $tWMI = Get-WmiObject Win32_OperatingSystem -ComputerName <<<<  $ExchangeServer.Name
    + CategoryInfo          : InvalidData: (:) [Get-WmiObject], ParameterBindingValidationException
    + FullyQualifiedErrorId : ParameterArgumentValidationError,Microsoft.PowerShell.Commands.GetWmiObjectCommand

You cannot call a method on a null-valued expression.
At C:\Users\dhadmin\Desktop\generateReport.ps1:324 char:68
+         $RUKeys= $RemoteRegistry.OpenSubKey($RegKey).GetSubKeyNames <<<< () | ForEach {"$RegKey\\$_"}
    + CategoryInfo          : InvalidOperation: (GetSubKeyNames:String) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

You cannot call a method on a null-valued expression.
At C:\Users\dhadmin\Desktop\generateReport.ps1:348 char:60
+         [array]$Roles = $ExchangeServer.ServerRole.ToString <<<< ().Replace(" ","").Split(",");
    + CategoryInfo          : InvalidOperation: (ToString:String) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

Cannot validate argument on parameter 'Server'. The argument is null or empty. Supply an argument that is not null or e
mpty and then try the command again.
    + CategoryInfo          : InvalidData: (:) [Get-Mailbox], ParameterBindingValidationException
    + FullyQualifiedErrorId : ParameterArgumentValidationError,Get-Mailbox

Cannot index into a null array.
At C:\Users\dhadmin\Desktop\generateReport.ps1:376 char:78
+         $ExchangeEnvironment["TotalMailboxesByVersion"][$tServer["Version"]][ <<<< "MailboxCount"]+=$tCount;
    + CategoryInfo          : InvalidOperation: (MailboxCount:String) [], RuntimeException
    + FullyQualifiedErrorId : NullArray

Cannot index into a null array.
At C:\Users\dhadmin\Desktop\generateReport.ps1:377 char:78
+         $ExchangeEnvironment["TotalMailboxesByVersion"][$tServer["Version"]][ <<<< "ServerCount"]++;
    + CategoryInfo          : InvalidOperation: (ServerCount:String) [], RuntimeException
    + FullyQualifiedErrorId : NullArray