Sometimes there is a connection error or problem with the EPEL repository. This will make all attempts to use YUM (The update and software installer for the Linux OS core) to fail with a message like: 

One of the configured repositories failed (Unknown)

The best way to handle this error is to add this to the end of any YUM commands:

--disablerepo=epel\*

For example: 

yum update --disablerepo=epel\*

Or another is: 

yum install softwarename -y --disablerepo=epel\*

This way you can use YUM right away. The epel REPOs are still there and active once the epel repositories are working again.