The illustration has been accepted, then, the day after, rejected

Probably because of your signature. (Watermark) Your asset can't have these types of details in it.

Non-compliant file
This reason means that your content doesn’t comply with our Contributor Agreement. Content may be non-compliant due to watermarks, inappropriate or irrelevant keywords or image titles, or questionable, or defamatory content. Your file is also rejected as non-compliant if you receive a reminder to submit a model or property release, or resolve a problem with a release, and you resubmit the file without addressing the issue.

https://helpx.adobe.com/stock/contributor/help/reasons-for-content-rejection.html