The version for tier 'release' is not defined!

Symptoms

upcp failed to download TIERS release with the following error:

Tried to sync version /etc/cpanel/TIERS.json file but failed: exit level [die] [pid=***] (Failed to download URL 'http://$IP/cpanelsync/TIERS.json.asc'.)

***** FATAL: The version for tier 'release' is not defined!

Description 

The issue is generated by the presence of /etc/cpsources.conf file which contain a wrong URL or IP address

Workaround

Remove the /etc/cpsources.conf or properly configure the file

Documentation

Installation Guide - Customize Your Installation