Thanks for letting us know about the activation issue that you are experiencing.
You can try performing a factory reset on your device. This will reset all settings and return your Roku device to a state ready for initial setup.
For more information on how to perform a factory reset, visit our Support page here: How do I factory reset my Roku® streaming device?
If you are still unable to get an activation code, we recommend rebooting both your wireless router and your Roku device