@chriswtsee Check this thread. You may try the OP solution to see if it will work for you.

@Ghazali Disable QoS if configured, also OneMesh and IPv6 if you don't use them.

@waxer1424 You can hard reset (method 1) the device and start over using the quick setup: Here's your user guide for details - Chapter 4:...

@DatD Reset to factory defaults and start over by using the quick setup: Here's the C20 user guide you could follow.

@VenuKumarBatta What's you main router make and model ? Interoperability between different brands is limited when using the range extender function. You can reset C50 to factory default and start...

@VenuKumarBatta Check if you have the operation mode Range Extender - if you do then switch the device to that mode: You can use this video for step by step configuration. If you don't have range...