Correct as Monnat mentioned the 3.4.0 version is actually a controller managed version, which means the AP is managed by a controller. So if you want to change it within this, you need to login to the controller itself.
if you want to use the AP now as standalone then the 104 or unleashed software should be used.
And to change from a controller managed version to Solo or Unleashed, you need to do a Hard Reset on your AP, reverting it to a 192.168.0.1 IP address, with super/sp-admin login credentials. Best to do this off your network.