Hi @Josemar and welcome to the forum 
We’ve checked and it doesn’t look like your IP range is being blocked, but it does look like you’re using an old version that is trying to reach a feed that no longer exists. The current release is GVM 21.04 and includes an updated openvas-scanner.
Also, the proxy may be an issue as the commercial product supports it (and usage of port 443) currently, but the community version does not. So please try syncing it without the proxy even after upgrading.
You can check the versions of the components here: New releases for GVM 20.08 and GVM 21.04 and please let us know after upgrading if that takes care of it. Thanks!
(edit to add- I may move some posts to a new thread later)