It looks like Let's Encrypt needs to be nudge on one of the servers
wget https://www.postgresql.org
--2021-10-08 15:24:33-- https://www.postgresql.org/
Resolving www.postgresql.org (www.postgresql.org) 87.238.57.232,
72.32.157.230, 217.196.149.50, ...
Connecting to www.postgresql.org
(www.postgresql.org)|87.238.57.232|:443... connected.
ERROR: cannot verify www.postgresql.org's certificate, issued by
‘/C=US/O=Let's Encrypt/CN=R3’:
Issued certificate has expired.
To connect to www.postgresql.org insecurely, use `--no-check-certificate'.