Hosting support did not solve the problem, because the error is not theirs and access by wget is good.

wget silently falls back to IPv4 if IPv6 fails. You can demonstrate this by forcing it to use IPv6 only:

Maybe you know what to check on the server to fix the error?

Maybe IPv6 networking isn't enabled at all or no global scope address has been assigned or there is no default route set up or ...

You will have to work with your hosting provider to determine the correct configuration details to use.