As a follow up to my last article regarding Microsoft Teams NEW Addin missing in Outlook https://www.ajni.it/2024/03/microsoft-teams-lightweight-teams-meeting-addin-in-outlook-missing/, this script might help you if there are still some issues especially on Terminal Services/RDS 2019/2022.

This script registers Microsoft.Teams.Addin.Loader.dll as the current user, so it has to run at logon.

if (-not ($NewTeamsPackageVersion = (Get-AppxPackage -Name MSTeams).Version)) {
Write-Host "New Teams Package not found. Please install new Teams from https://aka.ms/GetTeams ."
exit 1
}
Write-Host "Found new Teams Version: $NewTeamsPackageVersion"

$TMAPath = "{0}\WINDOWSAPPS\MSTEAMS_{1}_X64__8WEKYB3D8BBWE\MICROSOFTTEAMSMEETINGADDININSTALLER.MSI" -f $env:programfiles,$NewTeamsPackageVersion
if (-not ($TMAVersion = (Get-AppLockerFileInformation -Path $TMAPath | Select-Object -ExpandProperty Publisher).BinaryVersion))
{
Write-Host "Teams Meeting Addin not found in $TMAPath."
exit 1
}
Write-Host "Found Teams Meeting Addin Version: $TMAVersion"

$TMAParam= '/s /n /i:user "C:\Program Files (x86)\Microsoft\TeamsMeetingAddin{0}\x86\Microsoft.Teams.AddinLoader.dll"' -f $TMAVersion
Start-Process "C:\windows\System32\regsvr32.exe" -ArgumentList $TMAParam