Connection problems

Is your repeater capable of operating in both the 2.4 and the 5GHz WiFi network range? If not, you may have configured your 790 to the "wrong" band — check this inside of the 790's web admin interface. Also, because not all channels are allowed globally, a lot of devices of all kinds which operate in the 2.4GHz band don't support channels numbers larger than 11, so make sure your 790 doesn't use these. And make sure your repeater does also support the encryption type (WPA, WPA2, ...) and options that your 790 is set to.

If all this doesn't help, you'd need to provide more information about the repeater that you are trying to use (make, model, and the hardware and firmware versions if possible).