It is because your APs are mesh APs. You have to manually add them to the controller. Add the MAC address of the AP to MAC filter table. Follow this steps in GUI:
Security -> AAA -> Mac Filtering -> Mac Address
(wlc) >config macfilter add [interface name] [description] [Client IP address]
Once you complete this, APs should register to WLC in mesh mode, then you can convert them to any other AP mode you want.
You can find more explanation here.