Solution to Unity Asset Store "Open in Unity" button not working on Windows

Set-UnityAssetStoreProtocolHandler.ps1

$EditorRootPath = "C:\Program Files\Unity\Hub\Editor"
$versions = Get-ChildItem -Directory $EditorRootPath | Select-Object -Expand Name
$latestVersion = ($versions | Sort-Object -Descending | Select-Object -First 1)
$unityExe = Join-Path $EditorRootPath "$latestVersion\Editor\Unity.exe"
Write-Host "Try registering URL:com.unity3d.kharma for $unityExe"

Remove-Item -Path "Registry::HKEY_CLASSES_ROOT\UnityAssetStore" -Recurse -ErrorAction SilentlyContinue

New-Item -Path "Registry::HKEY_CLASSES_ROOT\UnityAssetStore" | Out-Null
New-Item -Path "Registry::HKEY_CLASSES_ROOT\UnityAssetStore\DefaultIcon" | Out-Null
New-Item -Path "Registry::HKEY_CLASSES_ROOT\UnityAssetStore\Shell" | Out-Null
New-Item -Path "Registry::HKEY_CLASSES_ROOT\UnityAssetStore\Shell\Open" | Out-Null  
New-Item -Path "Registry::HKEY_CLASSES_ROOT\UnityAssetStore\Shell\Open\Command" | Out-Null

Set-ItemProperty -Path "Registry::HKEY_CLASSES_ROOT\UnityAssetStore" `
    -Name "(Default)" -Value "URL:com.unity3d.kharma"
New-ItemProperty -Path "Registry::HKEY_CLASSES_ROOT\UnityAssetStore" `
    -Name "URL Protocol" -Value ""
Set-ItemProperty -Path "Registry::HKEY_CLASSES_ROOT\UnityAssetStore\DefaultIcon" `
    -Name "(Default)" -Value "'$unityExe',0"
Set-ItemProperty -Path "Registry::HKEY_CLASSES_ROOT\UnityAssetStore\Shell\Open" `
    -Name "FriendlyAppName" -Value "Unity $latestVersion"
Set-ItemProperty -Path "Registry::HKEY_CLASSES_ROOT\UnityAssetStore\Shell\Open\Command" `
    -Name "(Default)" -Value "'$unityExe' -openurl '%1'"

Write-Host "Registered successfully!"

Run powershell as administrator and execute these lines.