hi Xinxu,
two suggestions;
1) the IP address of the CDS has changed - see
CDS - IP range
Do your firewall settings need to be changed?
2) you are requesting surface data on a 0.25 degree grid; these data are available as pre-calculated CDS datasets - see: https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-single-levels?tab=overview
and these requests should run faster then requests to the era5-complete dataset.
Thanks,
Kevin