Ubuntu Invalid License File: YAML::Syck object version 1.34 does not match

Symptoms

WHM displays a "Invalid License File. Incorrect authority delivering the license" error.

License updates show the following error:

# /usr/local/cpanel/cpkeyclt
YAML::Syck object version 1.34 does not match $YAML::Syck::VERSION 1.36.

You may see errors like the following in the cPanel update logs.

[2025-10-17 02:50:07 +0000] W The “/usr/bin/dpkg --purge --force-all cpanel-postgresql” command (process 2620936) reported error number 2 when it ended. dpkg: error: dpkg frontend lock was locked by another process with pid 169922

Description

This is caused by APT package updates being locked up, which can result in some packages not being updated.

We've opened an internal case for our development team to investigate this further. For reference, the case number is CPANEL-49837. Follow this article to receive an email notification when a solution is published in the product. 

Workaround

1. Access your server using SSH as the root user.

2. Locate the running apt or dpkg process that is holding a lock on package updates:

   pgrep -f "apt|dkpg" -l

3. Using the process ID from the results above, kill the apt or dpkg process:

   kill $PID

4. Run the following script to check the cPanel packages and ensure everything is properly installed and updated:

   /scripts/check_cpanel_pkgs --fix

5. Update the license file to resolve the original error:

   /usr/local/cpanel/cpkeyclt