Hi Con!
Thank you for your support.
I have installed the plugin that you recommended, and indeed, the Emails are sent without a download link.
The problem product is not a copy from the other, I made it from scratch.
I still can’t find a solution. It’s really frustrating 🙁
Thank you @inesgraphiste and Hi @aetherong,
No solution for the moment. I installed a plugin to reverse the ELEMENTOR 2.5.5 update to 2.5.3 and everything is working perfectly again, so, it is an issue with this update.
The plugin that I used to reverse the update is here: https://ww.wp.xz.cn/plugins/wp-rollback/
Someone from the ELEMENTOR technical suppor contacted me to give me the same pre-established solutions that the error message from ELEMENTOR was giving me and that not solved anything at all.
Hope this helps.