Messages.txt file contains one or more lines starting with date and time followed by (substitute DatabaseName with the resource giving the UUconnect message):
UUconnect connect refused by DatabaseName.com:443 (10065 A socket operation was attempted to an unreachable host.) in DoTranslate
This indicates that EZproxy could not reach the remote host.
UUconnect errors point toward network connectivity or configuration issues. Common causes are:
Beyond that, things become site specific. If you have eliminated the above reasons, contact OCLC Support with the database name, the appropriate lines from the messages.txt file and exact steps to reproduce the error.