I've faced the problem with 5 GHz Wi-Fi on my hAP ac lite router. Suddenly it dissapeared on my PC. It wasn't that stable all the time I've used it but at least I could connect and I could use it.
Now I even don't see 5 GHz AP - only 2.4. Nothing changed. It just dissapeared.
I thought it was my ASUS Wi-Fi adapter to blame and change it for ASUS PCI-E adapter but it didn't see 5 GHz AP too.
Then I thought ASUS adapters are bad and bought TP-Link and it doesn't see 5 GHz AP too.
Besides, all of my smartphones - 3 Samsung Galaxy's - use 5 GHz just fine. 2.4 GHz is stable for all devices as far as I could check.
I don't know what is wrong for me - Windows 10 or Mikrotik but I've checked those adapters on my laptop and the result was the same - no 5 GHz AP.
Tried reset to defaults and even flash latest firmware with netinstall - nothing helped.
Ready to give you any info.
Here's my interfaces config:
[admin@MikroTik] > /interface wireless export # mar/12/2018 22:16:37 by RouterOS 6.41.2 # software id = YIL0-1FGX # # model = RouterBOARD 952Ui-5ac2nD /interface wireless security-profiles set [ find default=yes ] supplicant-identity=MikroTik add authentication-types=wpa2-psk eap-methods="" management-protection=allowed mode=dynamic-keys \ name=bro supplicant-identity="" wpa2-pre-shared-key=password /interface wireless set [ find default-name=wlan1 ] band=2ghz-b/g/n channel-width=20/40mhz-Ce disabled=no distance=\ indoors frequency=auto mode=ap-bridge security-profile=bro ssid=APName2 wireless-protocol=\ 802.11 wps-mode=disabled set [ find default-name=wlan2 ] band=5ghz-a/n/ac channel-width=20/40mhz-Ce country=russia2 disabled=\ no distance=indoors frequency=auto frequency-mode=regulatory-domain mode=ap-bridge \ security-profile=bro ssid=APName tx-power=11 tx-power-mode=all-rates-fixed \ wireless-protocol=unspecified wps-mode=disabled /interface wireless nstreme set wlan2 enable-polling=no