Since this morning I have had problems accessing my sites with Chrome on webserver.
My certificate is valid in the management of my domain name www.hgc63.fr, but chrome shows me the following message:
The website you are about to open is misleading
Malicious individuals at work on the www.hgc63.fr site could encourage you to carry out dangerous operations, such as installing software or disclosing personal information (passwords, telephone numbers or credit card numbers, for example ). Learn more.
I just migrated my server from a server with a different ip. My old IP was 22.214.171.124 and the new one is 126.96.36.199. I am not very comfortable with the management of certificates. Did I make a mistake creating a new certificate with the new IP address?
I wouldn't call it a "mistake", more "an opportunity to optimise". As you can see at https://crt.sh/?q=hgc63.fr&deduplicate=Y, you've issued multiple certificates with just a single hostname/subdomain incorporated in it. But you easily could have issued just a single certificate with all those subdomains in it, making it a lot more efficient, especially from the Let's Encrypt side (load et cetera).
And as said earlier, your site works fine, so that's good anyway.
There's no need to revoke previous certificates unless the private key has been leaked. (Some othe reasons apply, but it's not required in this situation.)
I don't know, as you haven't provided us the required information to answer that. There are multiple ways to get certificates as there are many, MANY clients out there capable of doing that and you haven't told us how you got the certificates in the first place.