I can no longer use the first four channels of the 5GHz band

[medwatt]

When I first got the AC66U_B1 router, I noticed that the 5GHz signal takes a long time before any of my devices can detect it. A member here suggested I should use channel 36 as channel 36 is not a DFS channel. This simple trick worked -- I could detect both bands simultaneously. However, today none of my devices were able to detect the 5GHz signal. I started changing channels and realized that I can't detect any signal when the channels are set to channels 36, 40, 44, 48. Channels 52, 56, 60, 64, and above all work, but there's a slight delay of about 2 minutes after the 2.4GHz signal is detected. I have no idea what is going on. Channels 36 to 48 are supposed to be the free channels. I live in an area that is completely devoid of 5GHz signals, so this is incredibly weird to me.

 

[ColinTaylor]

Duplicate post: https://www.snbforums.com/threads/can-no-longer-use-any-channels-in-band-a-uni-ii-lower.40194/