There are three known reasons:
(1) You're using 5Ghz Wi-Fi instead of 2.4 Ghz
(2) Distance between the Delta and router is further than 8 meters ( most case it works over 10 meters )
(3) The wifi channel of your router may be over 11 or in auto mode, recommended wifi channels are 1 to 10 for meeting international standards.
If non-above, please report your router's model name to us. And you can use wifi station mode while we figuring out how to let the Delta be compatible with your router. Please refer to Setting WiFi / AP mode of FLUX Delta with USB drive.