Hi @Junli_Zhang,
Welcome to the QIIME 2 forum!
There could be many causes for this, including firewall, transient server-side issues, or just because your query is too large.
You could test the first by seeing if a small query (e.g., specific sequence) works
You could test the second by just trying again and hoping it works this time!
But let's assume it's the third issue (too large).
Your query hits a lot of sequences in GenBank, including many full-length genomes.
You could try to focus your query a bit more, e.g., with a query like this: "txid7742[ORGN] AND 12S [TITLE] NOT mRNA[TITLE]"
that cuts down the number of sequences by about half, and drops the full-length genomes and predicted mRNA sequences (but maybe you want to keep those? I am making some assumptions), so that should limit the size of the data transfer.
Another option is to try to break up the query into batches if you can figure out a way to break it up, e.g., by downloading subclades separately.
You can see some related discussion here:
Please give that a try and let us know if you make any progress!