Hello,

I bought Mikrotik hAP ac and I have problem with 5 Ghz band. When I select "Czech Republic" in the list any device doesn't see my 5 Ghz Wifi LAN. But if I change country or select "no_country" Wifi works fine.

Can you help me ?

What frequency did the Wireless AP selected?

"Czech Republic" - 5735/20-Ce/ac
"no_country" - 5180/20-Ce/ac

you can manually specify the channel as well.
Your country has additional channels available 5735-5865Mhz and maybe your wireless client doesn't see those.