“Uploading custom apps is not allowed” When Instal

Question

Update: I just realized that I can install it if I download it and then bring it in via Apps > Upload a custom app, so it's only installing it from within App Studio that gives the error.

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I'm trying to work through the sample app at https://docs.microsoft.com/en-us/microsoftteams/platform/get-started/get-started-dotnet-app-studio, but I'm stuck at the part where you install it into Teams.

I get the error: "Uploading custom apps is not allowed."

According to Prepare your Office 365 tenant, in the admin center, under Settings > Services & add-ins > Microsoft Teams > Tenant-wide settings > Apps, I should turn on "Allow sideloading of external apps." In my tenant, that is indeed turned off:

But I can't turn it on. It's disabled, saying the settings have moved to the "Microsoft Teams & Skype for Business admin center."

In that admin center, I went to Teams apps > Permission policies. There, for "Global (Org-wide default), I have "allow all apps" for everything: .

For "Org-wide app settings", I have interaction with custom apps turned on: .

Under Setup policies > Global (Org-wide default), I have "Allow uploading custom apps" on: .

And I'm signed in as a user governed by that policy:

I'm stumped. What else do I need to do so that I can sideload a Teams app for development?

Answer 1

I had the same problem and it actually made me crazy especially because it may take a few hours to apply changes. Finally I was able to resolve the problem in the following way. I can imagine that certain steps are unnecessary but who knows.

1. By following instructions in the Manage app setup policies in Microsoft Teams, enable "Upload custom apps" in "Global (Org-wide default)".
2. Following same instructions created a custom setup policy with enabled "Upload custom apps".
3. Enable all permissions in "Global (Org-wide default)" as described in the Manage app permission policies in Microsoft Teams
4. Create a new permission policy with everything enabled.
5. Wait about an hour.
6. Assign these new policies to the user.
7. Make sure that everything what is mentioned in Manage custom app policies and settings in Microsoft Teams is enabled.
8. Wait another hour.
9. Quit desktop application, and start it again.

Now, finally, it works.