eclipse artifacts search depends on repository's index file, it seems, you did not download index file.
Check "Download repository index updates on start" and restart your eclipse.
And then, look at the progress view, an index file is downloading.
After downloading completely, your artifacts search feature is ready to use.
You also need to rebuild your maven repository index in 'maven repository view'.
In this view , open 'Global Repositories', right-click 'central', check 'Full Index Enable',
and then, click 'Rebuild Index' in the same menu.
A 66M index file will be downloaded.