5ghz not visible for android devices

Hi,

i have just setup our r7000 in our restaurant. We want to use the 2.4ghz for our admin and pos system and the 5ghz for guests. But only my laptop and my iPad can see the 5ghz ssid. My mobile phone supports 5ghz connection but cannot see the the ssid signal and neither can any of our android tablets. I have updated the latest firmware Firmware Version
V1.0.9.12_1.2.23 and reset a few times but still nothing. Is there anyone that can help us make our 5ghz signal visible for android devices?