Got PM - thanks.
Something seems to be wrong with your hosting environment.
Perhaps you should open a ticket with your host helpdesk.
Here is an outline of the problem.
During the installation of the CB 2.0 package one of the first items that is installed is the CBLib library.
This is placed in your Joomla root -> libraries folder in a CBLib subfolder.
The CBLib subfolder should have the following file also installed:
libraries/CBLib/CB/Legacy/Archive_Tar.php
but for some reason the environment is not letting this through.
I tried to manually uploaded it from my local repository using your cpanel access, but it did not succeed (no visible reason why).
I am attaching here a separate CBLib package that you can test with (and inform your hoster also).
Just try and install this on your website and verify that the libraries/CBLib/CB/Legacy/Archive_Tar.php file is never installed, but it should be (at least it is here on all my tests).
I am not a server expert but it could imply a corrupted filesystem or maybe a mod security issue.
Hoping you can clear this up with your hoster and post back info here.