File Vista Trial Version message

I use FileVistaControl with license key.
It's been working fine, but now displays the Trial Version message. 

Why does it occur?

I redeployed from development machine and now it seems to befine.

I saw similiar message from some other developer.

Thank You Very Much

The control caches the key so whenever you do a change on the key value, you need to restart application domain (via touching web.config).

Maybe the key was edited accidentally so the control got into trial mode.
Even if you fixed the key but you did not restart the application, the control couldn't notice the change.

I guess redeployment from your development machine caused a restart of the application so the control loaded the correct key again.