Thank you for your help !
cPanel now works OK.
But I must admit that after more than a week with an unresolved situation, I thought about changing host, and went back to my registrar's DNS.
Now that cPanel is rocking again, I want to change the DNS again to x10hosting.

But the
ZoneCheck test performed by my registrar fails and prevents your DNS from being used.
The fatal error is "Loopback is not resolvable".
Can you please correct this ?
If you also have the opportunity to fix the warnings too, I guess it would be even better.
Anyway thanks for your assistance !
Cobus.