A warm welcome here at the Roku Community, @Amaz!
Thanks for raising your concern with us regarding the excessive blinking of the blue light on your Roku Express 4K. As mentioned before, it could be an indication of an internet connection issue, and based on your response, it was not resolved by rebooting your router.
In this case, we highly suggest rebooting your Roku streaming device's system by navigating to your Home screen. Scroll up or down to select Settings > System > System restart.
If the issue still persists, please let us know, and we'll go from there.
Kind regards,
Carly
Carly Y.
Roku Community Moderator
