Welcome to the community, Quogayeel13
A permanent blinking white light on the WiFi Extender means it has lost the connection to your modem and is trying to reconnect.
Since it won’t connect right next to it, it might help to restart everything: you can unplug your modem and the extender, wait a moment, turn the modem back on first, and once it is fully online, plug the extender back in. Please wait at least 10 minutes for the automatic connection to finish.
If it still keeps blinking, the best option is to contact the hotline (0800 707 707) so they can check the activation in the background. Alternatively, if you have some patience, perhaps @Daniele_Sunrise can also take a look at it when he sees this.
For more details, you can also check the official guide: Sunrise WiFi Extender for Connect Boxes | Help
Cheerio, cosmo