Publish Online Error #40 in InDesign CC 2020

The Error I get is this:

An error occurred while uploading your document. Please try again.
Error #40
ID: 03f4db80-f385-11ea-9745-29e326bb180a

Hi everyone, this is my first post here.
I'm writing because I'm trying to post an InDesign file with Publish Online.
I'm using Adobe InDesign CC 2020 from a Windows 10.

I'll be honest, it's a fairly big file: 88 pages with text and high resolution images with links and interactivity.
The thing is I have uploaded the previous version (let's call it Version 1) with Publish Online and had no problems. Now I simply edited the text and created Version 2 and it won't upload. Even stranger, if I try uploading Version 1 again, it won't work either.

Note: I tried uploading another InDesign document (a 2 page CV) and had no problems.

Here's what I do.
I go to File - Publish Online.

The "Publish your document online" box opens up.
I set it up and click as you can see in the nex 2 images and click on the blue button PUBLISH.

A loading bar appears saying "Preparing your document to be published online" and loads succesfully. Here it is:

I then get another PUBLISH ONLINE box with a loading bar that says UPLOADING YOUR DOCUMENT. Here it is:

This bar never loads completely: it always stops at 91% and shows the message you found at the beginning of this post:

An error occurred while uploading your document. Please try again.
Error #40
ID: 03f4db80-f385-11ea-9745-29e326bb180a

I have already contacted the Adobe chat and they suggested the following (so far nothing worked):

1. Move pages to a new document and retry (dosen't solve it)
2. Try uploading a smaller range of pages (ex. pages 1-5, 5-10 and so on) until you find a group that doesn't work. That is the group that contains a page with problems. (tried it but all the smaller page groups work. If I then try uploading the entire file again it doesn't work)
3. Delete the last 10 pages and reupload (still won't work)
4. Send Package file to Adobe expert by email and wait for answer (I'm still waiting)
   
   Any suggestions?
   Thank you so much
   Francesco from Italy