@ Letot Jean-Jacques
Sorry to hear you are having trouble! There are no known conflicts with Elementor. I actually have it installed on my test site and works without any issues that I can find.
Elementor doe require quite a bit of resources, so, my best guess at the moment you are close to the limit of memory allocated to PHP and it just happens to be Connections, in this case, which puts you over that limit.
Please try this
Before doing the above, open an Elementor edit page in Chrome. Hit the F12 key and the click the Console tab. If there are errors being shown, what are they?