Mixedrealitytoolkit-unity: Unity 19.3.7f1 MRTK 2.4.0 can't connect HoloLens2 with Wi-Fi nor USB: NullReferenceException: DownloadHandler has already been destroyed

[FatherKingXWH]

Describe the bug

I can connect HoloLens2 with Wi-Fi using Chrome by ip address:192.168.0.102, and the Windows Device Portal shows correctly. (I also installed the certificate to make a trust connection)

But when I tried to connect it in Unity, it didn't work:

To reproduce

Steps to reproduce the behavior:

In Unity

1. Go to 'Mixed Reality Toolkit'
2. Go to 'Utilities'
3. Click on 'Bulid Window'
4. Click on 'Deploy Options'
5. Click on 'Target Type'

With Wi-Fi:

1. Scroll to 'Remote'
2. Type IpAddress, Username, Password
3. Clcik on 'Test Connection'
4. Unity Editor shows "NullReferenceException: DownloadHandler has already been destroyed"

With USB:

1. Scroll to 'Local'
2. Type Username, Password
3. Clcik on 'Test Connection'
4. Unity Editor shows "NullReferenceException: DownloadHandler has already been destroyed"

Expected behavior

How can I fixed it?

My setup

• Unity Version [v2019.3.7f1]
• MRTK Version [v2.4.0]
• win10 SDK[10.0.18362.1]

Target platform

• HoloLens 2

Additional context

In HoloLens2, "Developer Mode" and "Enable Device Portal" options are turned on

[keveleigh]

Fixed via https://github.com/microsoft/MixedRealityToolkit-Unity/pull/7823. Will ship in MRTK 2.4