The best thing to do is look at the output from the console of the access point. This will give you and us great information on what is going on. The other thing, are these ap's getting placed in the same site or a different site? Are the AP's on the same subnet as the existing ones? I say this, because there might be something blocking the join request or response.
Your best bet is to bring the AP's to the site that the WLC is on and connect them to the same vlan as the WLC management to prep them. Once they have joined, then you can move them to the location where they need to be installed.
Transferring Crash file from standby: Login to the Active WLC in HA.
From CLI: (Cisco Controller) >transfer upload datatype crash (Cisco
Controller) >transfer upload filename (Cisco
Controller) >transfer upload mode tftp (Cisco Controller) >transfer
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