Ok... DNS is pretty simple when you get right down to it.
If: <domain>.3cx.fr is the FQDN and the IP address 1.2.3.4 was teamed correctly in the initial setup, then the DNS record should point <domain>.3cx.fr to 1.2.3.4
If you do a dns lookup on <domain>.3cx.fr and it points to 1.2.3.4 then the entry is correct.
Here's where the fun starts.
If you have internal DNS servers that point <domain>.3cx.fr to another IP address (1.2.3.5 for example), and those DNS servers handle resolution requests for your network, then no matter how many times you want it to go to 1.2.3.4, it's going to go to 1.2.3.5 because your internal DNS servers say so.
If there was another entry (once upon a time) that used <domain>.3cx.fr as its fqdn and it was tied to 1.2.3.5, then that fqdn has been propagated to external DNS servers telling it to point that fqdn to that IP address. Which means you have to wait until 3CX DNS servers (who presumably are the NS for .3cx.fr) to push the updated name record out, and for the rest of the world's name servers to update their records from it - a process that can take up to 48 hours (or longer) depending on NS configurations. Generally, though, it's done pretty quickly.
A few things you can look at:
1. Make sure you're resolving to the right IP address.
2. Use a DNS lookup service on the internet somewhere else to see if your FQDN points to the right IP address. Check a few places.
3. Verify all of the setup information - the IP address bound to the FQDN through 3CX should have been sent to you in the admin email.
4. Try to browse to the ip address itself instead of the fqdn
5. Contact OVH and see if an alias is causing you all of this pain.
