In some countries like India, the usage of channels above 5825 MHz (channel 165) is allowed.
But the bounding of these channel (to permit 40 MHz channel) is a little bit particular and require a particular configuration:
The Channel-Pairing must be set to "legacy-turbo-friendly".
This setting is accessible via the web interface or via the CLI following this path:
HiLCO Menu Tree > Setup > Interfaces > WLAN > Radio-Settings > Channel-Pairing
Per default it's set to "11-n-compliant" and must then be modified.