Resolution: Not A Bug
i use nexus as maven repository proxy.
everything go well until recently i cannot download artifacts from nexus.
on repository status tab of Maven Central Repository, showing:
"In Service - Remote Automatically Blocked and Unavailable"
other repos proxy status is ok.
i emailed nexue supporter, and replied "maybe my'IP is blocked by maven central"
how to fix it. my public ip is : 18.104.22.168