I have installed in a Centos 5.4 server Virtualmin Version 3.76.gpl, and also have the file
/etc/virtualmin-license.txt with
SerialNumber=GPL
LicenseKey=GPL
Nevertheless when I click in ‘Virtualmin Package Updates’ I received the error:
An error occurred contacting the Virtualmin updates server : You do not have a Virtualmin license file
I have the same configuration in amazon EC2 and works perfect.