Hi,
You can change the email address from the PC Monitor Manager on the PC - it's not yet implemented on Linux. (send me a message and I can help with this one).
We made changes to the way the email address is validated, it should resolve the issue you were having.
When you created the account we activated a trial subscription so you can test the server modules. After that subscription expires you can still monitor your computers, only the server modules won't be available anymore.
Let me know if I can help.
Regards,
Marius