Solved
In my case, I was working with an image which I manually changed time ago from .webp to a .png, (typical case for ex. when downloading an image from DALL-E from OpenAI).
Te problem here is that even though you change it the format, and when you open it with a editor you will see a png image, the mime/type does not change.
The mime/types supported are: The mimeTypes which can be inserted to Google Docs are image/jpeg, image/png and image/gif. There conditions are the same for Spreadsheet, Document and Slides.
So, basically I did this:
And it worked out.
Hope this helps to other people!
