--no-check-certificate

while i was trying to run the “download-db.sh” command in my server, i was getting the following error:

Resolving data.gtdb.ecogenomic.org (data.gtdb.ecogenomic.org)... 203.101.230.53
Connecting to data.gtdb.ecogenomic.org (data.gtdb.ecogenomic.org)|203.101.230.53|:443... connected.
ERROR: cannot verify data.gtdb.ecogenomic.org's certificate, issued by ‘/C=US/O=Let's Encrypt/CN=R3’:
  Issued certificate has expired.
To connect to data.gtdb.ecogenomic.org insecurely, use `--no-check-certificate'.

can someone please tell me what is wrong.