Hi and thanks for taking interest in Vivvo
There shouldn't be any limitations to free trial, it should run full featured for 21 days.
So, there's definitely something wrong with your installation.
First, have you checked your server if it meets all requirements to run the Vivvo?
Second thing that comes to my mind is to check if all the files where copied properly.
Try re-uploading the script, and if that doesn't help, I suggest opening a support ticket with your FTP and admin access.