Some computers cannot connect to 5g wifi some can and wifi 2.4 G works for all?

RouterOS General
1

Hi there I have problem, some of my computers cannot connect to 5g wifi (my other computers can). All of them can connect to 2.4 g wifi.
What can I do the let all of them to reach the 5g wifi

I appreciate your help

2

Check if the used frequency is possible for those computers.
Try a lower channel.

3

Hi and thanks for the reply
how can I do this:
“Check if the used frequency is possible for those computers”
And how can I do this
“Try a lower channel”

Sorry in routers I am totally newbee
Thanks for your help