Hello,
In general similar message is generated if the printer is not activated or if it is activated using a wrong activation code?
Could it be that you are activating version 2.50 using an activation code for version 2.10?
Please check that there is no extra space at the end of the license key or activation code when activating the printer.
Try to reboot your system after installing the printer and activating it. If you still have this problem please send your activation code to support@amyuni.com to validate it, don't post your code to this forum because the activation code is confidential.
Hope this helps.