Maybe missing the 5GHz config. You can refer to this config:

# cat /etc/config/wireless 

config wifi-device 'radio0'
	option type 'mac80211'
	option channel '36'
	option hwmode '11a'
	option path 'pci0000:00/0000:00:00.0'
	option htmode 'VHT80'
	option txpower '15'
	option band '5G'
	option disabled '0'

config wifi-iface 'default_radio0'
	option device 'radio0'
	option network 'lan'
	option mode 'ap'
	option ssid 'GL-AR750-c8b-5G'
	option encryption 'psk-mixed'
	option key 'goodlife'
	option ifname 'wlan0'

config wifi-device 'radio1'
	option type 'mac80211'
	option channel '11'
	option path 'platform/qca953x_wmac'
	option htmode 'HT20'
	option hwmode '11ng'

config wifi-iface 'default_radio1'
	option device 'radio1'
	option network 'lan'
	option mode 'ap'
	option ssid 'GL-AR750-c8b'
	option encryption 'psk-mixed'
	option key 'goodlife'
	option wds '1'
	option ifname 'wlan1'