Hello
Due to the construction of the apartment, one of my working room is not in good coverage of the Wireless signal of the Speedport Smart 3, so I bought a EX3110 Netgear Wifi Extender and tried to install it for better coverage. 

During the first day of installation, the Extender worked perfectly and I can have better conncectivity in my working room. However, just after a few hours, the connectivity stopped, and I tried many times to connect the extender to the Speedport Smart 3, but could not. After upgrading the extender firmware and reset it, I could connect the second time to the Speedport router. This also lasted just a few hours before the connection between the extender and Speedport broke again.
After that I could not bring up the connection anymore.
I checked with the Speedport settings, but did not see whether the Extender MAC Address or anything to block the connection.
Please let me know how to fix it. I need this badly, as I have to move my laptop to another room for working and it is very inconvenient.

Thanks.