I try to delete some old APs which are moved to another WLC/Prime world or just the WLC was removed. I'm not sure what my colleauges did in Detail. But when I do it, the AP stay in the prime without an error message.
The AP is not Associated and not registerd, Audit Missmatch
Your question is old but I had quite a time finding the location to delete an AP from Prime 3.0 also. Click on the 3 line menu bar in the top left corner. Then hover over inventory and select Network Devices under the Device Management heading. Using the drop down Unified AP you can select all by just clicking the Unified AP or you can isolate the models by selecting the appropriate model under the Unified AP drop down. Select the AP you want to delete by placing a check mark in the box to the left op the AP. Once an AP, or many AP's) is/are selected the red X Delete at the top will be available to click. Hope this helps anyone else that had any issues finding the delete.