When trying to Sideload manually my office 365 outlook add-in on an Hotmail account I get those errors:

Installing error:

owa.mailindex.cbb81ec0.js:1 Uncaught (in promise) Error: InstallExtension failed: Unexpected token '<', "<?xml vers"... is not valid JSON

Uninstalling error:

Uncaught (in promise) Error: UninstallExtension failed: Microsoft.Exchange.Clients.Owa2.Server.Core.OwaServiceFaultException

I was previously able to install and use my add-in on this Hotmail account, but as of today I wasn’t able to.

Also, everything is working fine for every account in my organization, only my Hotmail account.

Are Hotmail accounts supported for add-ins?