Microsoft Add-In manifest doesn't work on outlook web

Question

I have developed a microsoft office add-in for outlook that can be seen here https://cdnqa.mcfile.com/mcoffice/manifest.outlook.xml

I have tested and it works as expected on local and production environment. I have validated the XMLs with the tool

office-addin-manifest validate

That yields a positive result for multiple platforms, including web:

Based on the requirements specified in your manifest, your add-in can run on the following platforms; your add-in will be tested on these platforms when you submit it to the Office Store:
  - Outlook 2013 or later on Windows
  - Outlook 2016 or later on Windows
  - Outlook 2019 or later on Windows
  - Outlook 2013 or later on Mac
  - Outlook 2016 or later on Mac
  - Outlook 2019 or later on Mac
  - Outlook on the web
  - Outlook on Windows (Microsoft 365)
  - Outlook on Mac (Microsoft 365)
Important: This analysis is based on the requirements specified in your manifest and does not account for any runtime JavaScript calls within your add-in. For information 
about which API sets and features are supported on each platform, see Office Add-in host and platform availability. (https://docs.microsoft.com/office/dev/add-ins/overview/office-add-in-availability).

*This does not include mobile apps. You can opt-in to support mobile apps when you submit your add-in.

The manifest is valid.

But when trying to open the taskpane I'm faced with the following error:

Note that this error do not exists on the desktop version. What is the cause or how can I debug this error?