Backup Script error: Cannot convert value to type System.String

Hi, Lately i have backups issues everywhere...Here is the newest one.

i User exactly the same script and more than one other farm.

This one SharePoint 2013 farm i get the following error in the failed mail:

Cannot convert value to type System.String

The Script

$ver = $host | select version

if ($ver.Version.Major -gt 1)  {$Host.Runspace.ThreadOptions = "ReuseThread"}

Add-PsSnapin Microsoft.SharePoint.Powershell –ErrorAction SilentlyContinue
#Add-PsSnapin Microsoft.SharePoint.Powershell

$TXTFile = "\\ServerName\sharepoint\SP2013_SiteCollection_Backups\mySites\SPContentDatabase_$today.txt" 

$List = "\\ServerName\sharepoint\SP2013_SiteCollection_Backups\mySites\List_$today.csv"

try 

{  

$today = (Get-Date -Format dd-MM-yyyy)

 

$webApplication = Get-SPWebApplication -Identity "http://Webapp.domain"

  foreach ($site in $webApplication.Sites) {                

      

    $backupPath = "\\Server\sharepoint\SP2013_SiteCollection_Backups\mySites\" +$Today+"_"+$site.OpenWeb()+".bak"

    Write-Host "Backing up $site to $backupPath"        

    Write-Host                 

    Add-Content -Path $List -Value "$($site.OpenWeb()).bak,$($site.Url)" 

    # backup the site        

    Backup-SPSite -Identity $site.Url -Path $backupPath  

  }         

 

# SEND MAIL.  

 

$emailFrom = "SPSuccessfull_Backups.domain.za"

$emailTo = "a email"

# Subject for the notification email. The + “$today” part will add the date in the subject.  

$subject = "The SharePoint SiteCollection Backup was Successful for "+"$today"

# Body or the notification email. The + “$today” part will add the date in the subject.  

$body = "The SharePoint Web Application was Successful for "+"$today"+". Please find attached is the database report."

 

$webapps = Get-SPWebApplication 

foreach($webapp in $webapps) 

{ 

    $ContentDatabases = $webapp.ContentDatabases 

    Add-Content -Path $TXTFile -Value "Content databases for $($webapp.url)" 

    foreach($ContentDatabase in $ContentDatabases) 

    { 

    $ContentDatabaseSize = [Math]::Round(($ContentDatabase.disksizerequired/1GB),2) 

    Add-Content -Path $TXTFile -Value "-     $($ContentDatabase.Name): $($ContentDatabaseSize)GB" 

    } 

} 

 

# IP address of your SMTP server. Make sure relay Is enabled for the SharePoint server on your SMTP server  

$smtpServer = "a IP"

#$smtp = new-object Net.Mail.SmtpClient($smtpServer)  

Send-MailMessage  -SmtpServer $smtpServer -From $emailFrom -To $emailTo -Subject $subject -Body $body -Attachment $TXTFile, $List

#$smtp.Send($emailFrom, $emailTo, $subject, $body) 

}

 

Catch

{  

$ErrorMessage = $_.Exception.Message  

# Configure the below parameters as per the above.  

$emailFrom = "SPFailed_@domain"

$emailTo = "a EMail" 


$subject = "The SharePoint Web Application Backup Job failed on "+"$today"  

$body = "The SharePoint Web Application Backup Job failed on "+"$today and the reason for failure was: $ErrorMessage."  

$smtpServer = "a IP" 

Send-MailMessage  -SmtpServer $smtpServer -From $emailFrom -To $emailTo -Subject $subject -Body $body

}