Can't connect to Internet every time computer wakes up or boots up.

I set my wifi Range extender with my computer running Window 10. Everything worked fine. But when I turn on the computer or when computer wakes up from sleep, it states that DNS is not found nor that I am not connected to Internet.  I had to keep rebooting extender in order to work again. I do not want to do that every time. So how to fix it so that computer will have access to internet without having to reboot extender.  

Thanks,