"Couldn't apply the scene. Try again later." error when trying to test a custom Together Mode scene

ChetanSharma-msft I'm following the document here: https://docs.microsoft.com/en-us/microsoftteams/platform/apps-in-teams-meetings/teams-together-mode

Here are the steps I'm following:

1. Open https://dev.teams.microsoft.com/scenes
2. Click on Default Scene under Create a scene
3. Click the View in Teams button in the upper-right
4. On the View in Teams screen, click Preview in Teams. This opens a Teams launcher webpage which in turns opens the Teams desktop app
5. In the Teams desktop app, a popup appears for the "Default Scene" app which displays a warning that this app isn't from your org's app catalog or the Teams store. After a few seconds, an Add button appears. Click the Add button
6. Once the app has been added, join a meeting with multiple participants with their video turned on
7. Click the three dots button in the meeting window and choose Together Mode
8. Click the Change Scene button in the lower left
9. From the list of scenes, select the newly added Default Scene from the list

Expected result: The newly added scene is displayed

Actual result: A purple banner appears along the top of the meeting window saying "Couldn't apply the scene. Try again later."