SQL Monitor trial licenses can only be applied if the trial license is the only license being used. This means that if you have already purchased and activated a SQL Monitor or SQL Toolbelt license you will need to remove this license before applying your trial license.
Enter the trial license serial number on the configuration page:
Go to the Configuration tab and, under Licensing, select Licensing:
Select Activate a perpetual license and enter your serial key for your trial extension and click Activate.
A SQL Monitor trial license will not show up on your configuration page. You will not see the license number or how many servers the license covers. You may notice that your configuration page reads Number of licenses '0'.
Now you can start adding your servers. See, Adding servers for monitoring