There could be several reasons for this:
• does your router switch off overnight to save power?
• have you reached the limit of connected devices?
• Is your network protected, so you need to store the robot’s MAC address in the router?
• have you set up a special child lock?
In general, the robot only works on a 2.4 gigahertz network. So, please check whether your router perhaps only transmits on 5 gigahertz.
If you are in any doubt, you can also try to connect the robot via a hotspot on a smartphone.
Here is a video guide: