New MSTeams Failed to Install Microsoft Teams Addin for Outlook – Let’s Get It Back!

There have been recent reports of the new MSTeams upgrade failing to install the Microsoft Teams Addin for Outlook. Users in This Microsoft forum discuss a solution by simply uninstalling the add-in, then closing and reopening MSTeams and Outlook. This solution certainly works, and you could email affected users an SOP that outlines these steps and have them repair it. This is possible because the Microsoft Teams Outlook Add-in should be installed in the user context, so the standard account has the permissions to uninstall it.

Scripting Microsoft’s Workaround with PowerShell

In an enterprise environment, its preferred to find and deploy a solution to all affected workstations, so I created a simple solution that can be deployed via an Intune remediation script or packaged as a win32 app. This is the simple detection script that searches for any incorrect configuration. Please send me a comment if I am missing something.

Detecting if New MSTeams and Plugin are Installed

$regPath = "HKCU:\Software\Microsoft\Office\Outlook\Addins\TeamsAddin.FastConnect"
$teamsAddinLocalPath = "$($env:LOCALAPPDATA)\Microsoft\TeamsMeetingAddin"

# guard
if($null -eq (Get-AppxPackage -name MSTeams)){
    Write-Output "New MSTeams AppxPackage was not detected. Exit 0"; exit 0
}
    
if( -not (Test-Path $teamsAddinLocalPath) ){
    Write-Output "Teams Addin path not detected. Exit 1"; exit 1
}

if( -not (test-path $regPath) ){
    Write-Output "$regPath not detected. Exit 1"; exit 1
}

$regValue = Get-ItemPropertyValue -path $regPath -Name "LoadBehavior" -ErrorAction SilentlyContinue

if($regValue -ne 3){
    Write-Output "$regPath contains WRONG value of $regValue. Exit 1"; exit 1
}

Write-Output "TeamsAddin.FastConnect is installed properly. Exit 0"; exit 0

This checks if the new MSTeams is installed, and the path and registry keys are correct. I retrieved this information from Another Microsoft Forum and the add-in still uses the same registry path. Now let’s check out the remediation script. This is performing the same tasks the users otherwise would – uninstalling add-in, terminating processes, and validating new install – but as a PowerShell script.

Remediating MSTeams Outlook Addin

$ErrorActionPreference = "SilentlyContinue"
$regTeamsAddin = "HKCU:\Software\Microsoft\Office\Outlook\Addins\TeamsAddin.FastConnect\"

$obj = Get-WmiObject -Class win32_product -Filter "Name = 'Microsoft Teams Meeting Add-in for Microsoft Office'"

if($null -ne $obj){
    write-output "Uninstalling $($obj.Name)"
    $obj.Uninstall() | Out-Null
}

$proc = Get-Process -Name ms-teams, OUTLOOK
$sProc = stop-process -InputObject $proc -Force

$tp = Start-Process -FilePath ms-teams.exe -PassThru

do{
    # write-output "waiting for the teams process to start."
    Start-Sleep -Seconds 3
    if($null -ne $tp){ break }

}while($null -eq $tp)

Start-Sleep -Seconds 3

if((Get-ItemPropertyValue -Path $regTeamsAddin -Name "LoadBehavior") -eq 3){
    write-output "$($obj.Name) installed correctly. Exit 0"; exit 0
}

Write-Output "Teams Meeting Addin failed to load. exit 1"; Exit 1

This script fetches the software data from WMI, then uses the built-in Uninstall() method from Get-WMIObject command. After the uninstall, it terminates the ms-teams and outlook processes, then re-launches MSTeams. Upon starting new MSTeams, it should re-install the Microsoft Teams Addin for Outlook, then it looks for the registry item property value and exits.

Conclusion

Because this can become an issue in large environments affecting many people as they upgrade from the Classic Teams, I decided to script a solution. Although this isn’t perfect it should get the job done. We hope Microsoft releases MSTeams patches to resolve this issue, but this is something to use until it’s fixed. You can certainly improve the script and leave a comment with your solution or Contact me.