On my RB3011 I can easily check for RouterOS update, but when I check for updates on the attached Wap AC I get error: could not resolve dnd name. The Wap AC has the same DNS servers configured as the RB3011. So what is wrong? I have perfect internet connectivity on my laptop which is wirelessly connected to the Wap AC without DNS problems.
Check that the wAP AC has a route to the internet ie: 0.0.0.0.
How is your wAP ac configured?
Can you post IP information?